diff --git a/md/step4.md b/md/step4.md
new file mode 100644
index 000000000..5e863ca82
--- /dev/null
+++ b/md/step4.md
@@ -0,0 +1,29 @@
+# 🚀 4단계 - 수강신청(요구사항 변경)
+
+## 핵심 학습 목표
+
+- DB 테이블이 변경될 때도 스트랭글러 패턴을 적용해 점진적인 리팩터링을 연습한다.
+    - [스트랭글러(교살자) 패턴 - 마틴 파울러](https://martinfowler.com/bliki/StranglerFigApplication.html)
+    - [스트랭글러 무화과 패턴](https://docs.microsoft.com/ko-kr/azure/architecture/patterns/strangler-fig)
+
+<br>
+
+## 변경된 기능 요구사항
+### **강의 수강신청은 강의 상태가 모집중일 때만 가능하다.**
+- [X] 강의가 진행 중인 상태에서도 수강신청이 가능해야 한다.
+    - 강의 진행 상태(준비중, 진행중, 종료)와 모집 상태(비모집중, 모집중)로 상태 값을 분리해야 한다.
+
+### **강의는 강의 커버 이미지 정보를 가진다.**
+- [X] 강의는 **하나 이상**의 커버 이미지를 가질 수 있다.
+
+### 강사가 승인하지 않아도 수강 신청하는 모든 사람이 수강 가능하다.
+- [ ] 우아한테크코스(무료), 우아한테크캠프 Pro(유료)와 같이 선발된 인원만 수강 가능해야 한다.
+    - [ ] 강사는 수강신청한 사람 중 선발된 인원에 대해서만 수강 승인이 가능해야 한다.
+    - [ ] 강사는 수강신청한 사람 중 선발되지 않은 사람은 수강을 취소할 수 있어야 한다.
+
+<br>
+
+## 프로그래밍 요구사항
+- 리팩터링할 때 컴파일 에러와 기존의 단위 테스트의 실패를 최소화하면서 점진적인 리팩터링이 가능하도록 한다.
+- DB 테이블에 데이터가 존재한다는 가정하에 리팩터링해야 한다.
+    - 즉, 기존에 쌓인 데이터를 제거하지 않은 상태로 리팩터링 해야 한다.
diff --git a/src/main/java/nextstep/courses/domain/CoverImages.java b/src/main/java/nextstep/courses/domain/CoverImages.java
new file mode 100644
index 000000000..969834ad1
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/CoverImages.java
@@ -0,0 +1,21 @@
+package nextstep.courses.domain;
+
+import nextstep.courses.exception.EmptyCoverImageException;
+
+import java.util.List;
+
+public class CoverImages {
+
+    private List<CoverImage> images;
+
+    public CoverImages(List<CoverImage> images) {
+        validateIsNull(images);
+        this.images = images;
+    }
+
+    private void validateIsNull(List<CoverImage> images) {
+        if (images == null || images.isEmpty()) {
+            throw new EmptyCoverImageException();
+        }
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/Period.java b/src/main/java/nextstep/courses/domain/Period.java
index f57b036fb..b5a4d9606 100644
--- a/src/main/java/nextstep/courses/domain/Period.java
+++ b/src/main/java/nextstep/courses/domain/Period.java
@@ -25,10 +25,6 @@ private void validatePeriod(LocalDate startDate, LocalDate endDate) {
         }
     }
 
-    public boolean isDateWithinRange(LocalDate date) {
-        return !date.isBefore(startDate) && !date.isAfter(endDate);
-    }
-
     public LocalDate startDate() {
         return startDate;
     }
diff --git a/src/main/java/nextstep/courses/domain/RecruitmentStatus.java b/src/main/java/nextstep/courses/domain/RecruitmentStatus.java
new file mode 100644
index 000000000..c39f26c24
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/RecruitmentStatus.java
@@ -0,0 +1,27 @@
+package nextstep.courses.domain;
+
+import nextstep.courses.exception.InvalidRecruitmentStatusException;
+
+import java.util.Arrays;
+
+public enum RecruitmentStatus {
+    NOT_RECRUITMENT,
+    RECRUITING;
+
+    private static final RecruitmentStatus[] VALUES = values();
+
+    public static RecruitmentStatus findByName(String name) {
+        return Arrays.stream(VALUES)
+                .filter(status -> status.name().equalsIgnoreCase(name))
+                .findFirst()
+                .orElseThrow(() -> new InvalidRecruitmentStatusException(name));
+    }
+
+    public RecruitmentStatus ofRecruiting() {
+        return RECRUITING;
+    }
+
+    public boolean isRecruiting() {
+        return this == RECRUITING;
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 2a12b369b..69e826883 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -1,8 +1,6 @@
 package nextstep.courses.domain;
 
 import nextstep.courses.exception.InvalidSessionException;
-import nextstep.courses.exception.NotOpenSessionException;
-import nextstep.courses.exception.OutOfSessionException;
 import nextstep.payments.domain.Payment;
 
 import java.time.LocalDate;
@@ -13,39 +11,39 @@ public class Session extends BaseEntity {
     private final Long id;
     private final Long courseId;
     private final SessionType type;
-    private final CoverImage coverImage;
+    private final CoverImages coverImages;
     private final Period period;
-    private Status status;
+    private final Status status;
     private final Students students;
     private final PaidCondition paidCondition;
 
-    public static Session ofFree(Long id, Long courseId, CoverImage coverImage, LocalDate startDate, LocalDate endDate) {
-        return new Session(id, courseId, SessionType.FREE, coverImage, new Period(startDate, endDate), Status.NOT_OPEN, 0, 0L, LocalDateTime.now(), null);
+    public static Session ofFree(Long id, Long courseId, CoverImages coverImages, LocalDate startDate, LocalDate endDate) {
+        return new Session(id, courseId, SessionType.FREE, coverImages, new Period(startDate, endDate), new Status(LocalDate.now(), startDate, endDate), 0, 0L, LocalDateTime.now(), null);
     }
 
-    public static Session ofPaid(Long id, Long courseId, CoverImage coverImage, LocalDate startDate, LocalDate endDate, int maxStudents, Long fee) {
-        return new Session(id, courseId, SessionType.PAID, coverImage, new Period(startDate, endDate), Status.NOT_OPEN, maxStudents, fee, LocalDateTime.now(), null);
+    public static Session ofPaid(Long id, Long courseId, CoverImages coverImages, LocalDate startDate, LocalDate endDate, int maxStudents, Long fee) {
+        return new Session(id, courseId, SessionType.PAID, coverImages, new Period(startDate, endDate), new Status(LocalDate.now(), startDate, endDate), maxStudents, fee, LocalDateTime.now(), null);
     }
 
-    public static Session of(Long id, Long courseId, SessionType type, CoverImage coverImage, Status status, LocalDate startDate, LocalDate endDate, int maxStudents, Long fee, LocalDateTime createdAt, LocalDateTime updatedAt) {
-        return new Session(id, courseId, type, coverImage, new Period(startDate, endDate), status, maxStudents, fee, createdAt, updatedAt);
+    public static Session of(Long id, Long courseId, SessionType type, CoverImages coverImages, RecruitmentStatus recruitmentStatus, LocalDate startDate, LocalDate endDate, int maxStudents, Long fee, LocalDateTime createdAt, LocalDateTime updatedAt) {
+        return new Session(id, courseId, type, coverImages, new Period(startDate, endDate), new Status(LocalDate.now(), startDate, endDate, recruitmentStatus), maxStudents, fee, createdAt, updatedAt);
     }
 
-    private Session(Long id, Long courseId, SessionType type, CoverImage coverImage, Period period, Status status, int maxStudents, Long fee, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    private Session(Long id, Long courseId, SessionType type, CoverImages coverImages, Period period, Status status, int maxStudents, Long fee, LocalDateTime createdAt, LocalDateTime updatedAt) {
         super(createdAt, updatedAt);
-        validateNotNull(id, coverImage, period);
+        validateNotNull(id, coverImages, period);
         this.id = id;
         this.courseId = courseId;
         this.type = type;
-        this.coverImage = coverImage;
+        this.coverImages = coverImages;
         this.period = period;
         this.status = status;
         this.students = new Students();
         this.paidCondition = new PaidCondition(maxStudents, fee);
     }
 
-    private void validateNotNull(Long id, CoverImage coverImage, Period period) {
-        if (id == null || coverImage == null || period == null) {
+    private void validateNotNull(Long id, CoverImages coverImages, Period period) {
+        if (id == null || coverImages == null || period == null) {
             throw new InvalidSessionException();
         }
     }
@@ -59,20 +57,11 @@ public void register(Payment payment) {
     }
 
     protected void validateStatus() {
-        if (!status.isOpen()) {
-            throw new NotOpenSessionException();
-        }
-    }
-
-    public void openSession() {
-        if (!period.isDateWithinRange(LocalDate.now())) {
-            throw new OutOfSessionException();
-        }
-        changeStatusOpen();
+        this.status.validate();
     }
 
-    private void changeStatusOpen() {
-        this.status = status.ofOpen();
+    public void startRecruiting() {
+        this.status.startRecruiting();
     }
 
     public Long id() {
@@ -83,16 +72,16 @@ public Long courseId() {
         return courseId;
     }
 
-    public Long imageId() {
-        return coverImage.getId();
-    }
-
     public String type() {
         return type.name();
     }
 
-    public String status() {
-        return status.name();
+    public String sessionStatus() {
+        return status.sessionStatus();
+    }
+
+    public String recruitmentStatus() {
+        return status.recruitmentStatus();
     }
 
     public LocalDate startDate() {
@@ -115,8 +104,9 @@ public Long fee() {
     public String toString() {
         return "Session{" +
                 "id=" + id +
+                ", courseId=" + courseId +
                 ", type=" + type +
-                ", coverImage=" + coverImage +
+                ", coverImages=" + coverImages +
                 ", period=" + period +
                 ", status=" + status +
                 ", students=" + students +
diff --git a/src/main/java/nextstep/courses/domain/SessionStatus.java b/src/main/java/nextstep/courses/domain/SessionStatus.java
new file mode 100644
index 000000000..8138217b0
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionStatus.java
@@ -0,0 +1,25 @@
+package nextstep.courses.domain;
+
+import java.time.LocalDate;
+
+public enum SessionStatus {
+    PREPARING,
+    IN_PROGRESS,
+    COMPLETED;
+
+    public static SessionStatus of(LocalDate now, LocalDate startDate, LocalDate endDate) {
+        if (now.isBefore(startDate)) {
+            return PREPARING;
+        }
+
+        if (now.isAfter(startDate) && now.isBefore(endDate)) {
+            return IN_PROGRESS;
+        }
+
+        return COMPLETED;
+    }
+
+    public boolean isInProgress() {
+        return this == IN_PROGRESS;
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/Status.java b/src/main/java/nextstep/courses/domain/Status.java
index fec47173b..578e80a91 100644
--- a/src/main/java/nextstep/courses/domain/Status.java
+++ b/src/main/java/nextstep/courses/domain/Status.java
@@ -1,27 +1,42 @@
 package nextstep.courses.domain;
 
-import nextstep.courses.exception.InvalidSessionStatusException;
+import nextstep.courses.exception.NotOpenSessionException;
 
-import java.util.Arrays;
+import java.time.LocalDate;
 
-public enum Status {
-    NOT_OPEN,
-    OPEN,
-    CLOSED;
+public class Status {
 
+    private SessionStatus sessionStatus;
+    private RecruitmentStatus recruitmentStatus;
 
-    public Status ofOpen() {
-        return OPEN;
+    public Status(LocalDate now, LocalDate startDate, LocalDate endDate) {
+        this(SessionStatus.of(now, startDate, endDate), RecruitmentStatus.NOT_RECRUITMENT);
     }
 
-    public boolean isOpen() {
-        return this == OPEN;
+    public Status(LocalDate now, LocalDate startDate, LocalDate endDate, RecruitmentStatus recruitmentStatus) {
+        this(SessionStatus.of(now, startDate, endDate), recruitmentStatus);
     }
 
-    public static Status findByName(String name) {
-        return Arrays.stream(values())
-                .filter(status -> status.name().equalsIgnoreCase(name))
-                .findFirst()
-                .orElseThrow(() -> new InvalidSessionStatusException(name));
+    public Status(SessionStatus sessionStatus, RecruitmentStatus recruitmentStatus) {
+        this.sessionStatus = sessionStatus;
+        this.recruitmentStatus = recruitmentStatus;
+    }
+
+    public void validate() {
+        if (!sessionStatus.isInProgress() && !recruitmentStatus.isRecruiting()) {
+            throw new NotOpenSessionException();
+        }
+    }
+
+    public void startRecruiting() {
+        this.recruitmentStatus = recruitmentStatus.ofRecruiting();
+    }
+
+    public String sessionStatus() {
+        return this.sessionStatus.name();
+    }
+
+    public String recruitmentStatus() {
+        return this.recruitmentStatus.name();
     }
 }
diff --git a/src/main/java/nextstep/courses/exception/EmptyCoverImageException.java b/src/main/java/nextstep/courses/exception/EmptyCoverImageException.java
new file mode 100644
index 000000000..49d5a79b8
--- /dev/null
+++ b/src/main/java/nextstep/courses/exception/EmptyCoverImageException.java
@@ -0,0 +1,8 @@
+package nextstep.courses.exception;
+
+public class EmptyCoverImageException extends RuntimeException {
+
+    public EmptyCoverImageException() {
+        super("강의는 하나 이상의 커버 이미지를 가져야 합니다.");
+    }
+}
diff --git a/src/main/java/nextstep/courses/exception/InvalidRecruitmentStatusException.java b/src/main/java/nextstep/courses/exception/InvalidRecruitmentStatusException.java
new file mode 100644
index 000000000..10067cd5a
--- /dev/null
+++ b/src/main/java/nextstep/courses/exception/InvalidRecruitmentStatusException.java
@@ -0,0 +1,8 @@
+package nextstep.courses.exception;
+
+public class InvalidRecruitmentStatusException extends RuntimeException {
+
+    public InvalidRecruitmentStatusException(String code) {
+        super("존재하지 않는 강의 모집 상태입니다." + code);
+    }
+}
diff --git a/src/main/java/nextstep/courses/exception/InvalidSessionStatusException.java b/src/main/java/nextstep/courses/exception/InvalidSessionStatusException.java
deleted file mode 100644
index 2411415f8..000000000
--- a/src/main/java/nextstep/courses/exception/InvalidSessionStatusException.java
+++ /dev/null
@@ -1,8 +0,0 @@
-package nextstep.courses.exception;
-
-public class InvalidSessionStatusException extends RuntimeException {
-
-    public InvalidSessionStatusException(String code) {
-        super("존재하지 않는 강의 상태입니다." + code);
-    }
-}
diff --git a/src/main/java/nextstep/courses/exception/NotOpenSessionException.java b/src/main/java/nextstep/courses/exception/NotOpenSessionException.java
index acad19812..68ada8d5a 100644
--- a/src/main/java/nextstep/courses/exception/NotOpenSessionException.java
+++ b/src/main/java/nextstep/courses/exception/NotOpenSessionException.java
@@ -2,6 +2,6 @@
 
 public class NotOpenSessionException extends RuntimeException {
     public NotOpenSessionException() {
-        super("모집 중인 강의가 아닙니다.");
+        super("진행 중이거나 모집 중인 강의가 아닙니다.");
     }
 }
diff --git a/src/main/java/nextstep/courses/infrastructure/JdbcCoverImageRepository.java b/src/main/java/nextstep/courses/infrastructure/JdbcCoverImageRepository.java
index 3210c0491..aaa84a932 100644
--- a/src/main/java/nextstep/courses/infrastructure/JdbcCoverImageRepository.java
+++ b/src/main/java/nextstep/courses/infrastructure/JdbcCoverImageRepository.java
@@ -8,6 +8,7 @@
 
 import java.sql.Timestamp;
 import java.time.LocalDateTime;
+import java.util.List;
 
 @Repository("coverImageRepository")
 public class JdbcCoverImageRepository implements CoverImageRepository {
@@ -19,23 +20,33 @@ public JdbcCoverImageRepository(JdbcOperations jdbcTemplate) {
     }
 
     @Override
-    public int save(CoverImage image) {
-        String sql = "insert into cover_image (id, size, extension, width, height, created_at) values(?, ?, ?, ?, ?, ?)";
-        return jdbcTemplate.update(sql, image.getId(), image.getSize(), image.getExtension(), image.getWidth(), image.getHeight(), image.getCreatedAt());
+    public int save(CoverImage image, Long sessionId) {
+        String sql = "insert into cover_image (id, session_id, size, extension, width, height, created_at) values(?, ?, ?, ?, ?, ?, ?)";
+        return jdbcTemplate.update(sql, image.getId(), sessionId, image.getSize(), image.getExtension(), image.getWidth(), image.getHeight(), image.getCreatedAt());
     }
 
     @Override
     public CoverImage findById(Long id) {
-        String sql = "select id, size, extension, width, height, created_at, updated_at from cover_image where id = ?";
+        String sql = "select id, session_id, size, extension, width, height, created_at, updated_at from cover_image where id = ?";
+        return jdbcTemplate.queryForObject(sql, rowMapper(), id);
+    }
+
+    @Override
+    public List<CoverImage> findAllBySessionId(Long id) {
+        String sql = "select id, session_id, size, extension, width, height, created_at, updated_at from cover_image where session_id = ?";
+        return jdbcTemplate.query(sql, rowMapper(), id);
+    }
+
+    private RowMapper<CoverImage> rowMapper() {
         RowMapper<CoverImage> rowMapper = (rs, rowNum) -> new CoverImage(
                 rs.getLong(1),
-                rs.getLong(2),
-                rs.getString(3),
-                rs.getInt(4),
+                rs.getLong(3),
+                rs.getString(4),
                 rs.getInt(5),
-                toLocalDateTime(rs.getTimestamp(6)),
-                toLocalDateTime(rs.getTimestamp(7)));
-        return jdbcTemplate.queryForObject(sql, rowMapper, id);
+                rs.getInt(6),
+                toLocalDateTime(rs.getTimestamp(7)),
+                toLocalDateTime(rs.getTimestamp(8)));
+        return rowMapper;
     }
 
     private LocalDateTime toLocalDateTime(Timestamp timestamp) {
diff --git a/src/main/java/nextstep/courses/infrastructure/JdbcSessionRepository.java b/src/main/java/nextstep/courses/infrastructure/JdbcSessionRepository.java
index 755df2281..cd6bb4add 100644
--- a/src/main/java/nextstep/courses/infrastructure/JdbcSessionRepository.java
+++ b/src/main/java/nextstep/courses/infrastructure/JdbcSessionRepository.java
@@ -1,9 +1,9 @@
 package nextstep.courses.infrastructure;
 
-import nextstep.courses.domain.CoverImage;
+import nextstep.courses.domain.CoverImages;
+import nextstep.courses.domain.RecruitmentStatus;
 import nextstep.courses.domain.Session;
 import nextstep.courses.domain.SessionType;
-import nextstep.courses.domain.Status;
 import nextstep.courses.repository.CoverImageRepository;
 import nextstep.courses.repository.SessionRepository;
 import org.springframework.jdbc.core.JdbcOperations;
@@ -29,25 +29,25 @@ public JdbcSessionRepository(JdbcOperations jdbcTemplate) {
 
     @Override
     public int save(Session session) {
-        String sql = "insert into session (id, course_id, image_id, type, status, start_date, end_date, max_students, fee, created_at) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
-        return jdbcTemplate.update(sql, session.id(), session.courseId(), session.imageId(), session.type(), session.status(), session.startDate(), session.endDate(), session.maxStudents(), session.fee(), session.getCreatedAt());
+        String sql = "insert into session (id, course_id, type, recruitment_status, start_date, end_date, max_students, fee, created_at) values (?, ?, ?, ?, ?, ?, ?, ?, ?)";
+        return jdbcTemplate.update(sql, session.id(), session.courseId(), session.type(), session.recruitmentStatus(), session.startDate(), session.endDate(), session.maxStudents(), session.fee(), session.getCreatedAt());
     }
 
     @Override
     public Session findById(Long id) {
-        String sql = "select id, course_id, type, image_id, status, start_date, end_date, max_students, fee, created_at, updated_at from session where id = ?";
+        String sql = "select id, course_id, type, recruitment_status, start_date, end_date, max_students, fee, created_at, updated_at from session where id = ?";
         RowMapper<Session> rowMapper = (rs, rowNum) -> Session.of(
                 rs.getLong(1),
                 rs.getLong(2),
                 SessionType.findByCode(rs.getString(3)),
-                coverImage(rs.getLong(4)),
-                Status.findByName(rs.getString(5)),
+                coverImages(id),
+                RecruitmentStatus.findByName(rs.getString(4)),
+                toLocalDate(rs.getDate(5)),
                 toLocalDate(rs.getDate(6)),
-                toLocalDate(rs.getDate(7)),
-                rs.getInt(8),
-                rs.getLong(9),
-                toLocalDateTime(rs.getTimestamp(10)),
-                toLocalDateTime(rs.getTimestamp(11)));
+                rs.getInt(7),
+                rs.getLong(8),
+                toLocalDateTime(rs.getTimestamp(9)),
+                toLocalDateTime(rs.getTimestamp(10)));
 
         return jdbcTemplate.queryForObject(sql, rowMapper, id);
     }
@@ -66,7 +66,7 @@ private LocalDate toLocalDate(Date date) {
         return date.toLocalDate();
     }
 
-    private CoverImage coverImage(Long id) {
-        return coverImageRepository.findById(id);
+    private CoverImages coverImages(Long id) {
+        return new CoverImages(coverImageRepository.findAllBySessionId(id));
     }
 }
diff --git a/src/main/java/nextstep/courses/infrastructure/JdbcStudentsRepository.java b/src/main/java/nextstep/courses/infrastructure/JdbcStudentsRepository.java
index 147c958cb..eecc3c403 100644
--- a/src/main/java/nextstep/courses/infrastructure/JdbcStudentsRepository.java
+++ b/src/main/java/nextstep/courses/infrastructure/JdbcStudentsRepository.java
@@ -5,8 +5,12 @@
 import nextstep.users.domain.NsUser;
 import org.springframework.jdbc.core.JdbcOperations;
 import org.springframework.jdbc.core.RowMapper;
+import org.springframework.jdbc.support.GeneratedKeyHolder;
+import org.springframework.jdbc.support.KeyHolder;
 import org.springframework.stereotype.Repository;
 
+import java.sql.PreparedStatement;
+import java.sql.Timestamp;
 import java.time.LocalDateTime;
 import java.util.Set;
 
@@ -20,22 +24,40 @@ public JdbcStudentsRepository(JdbcOperations jdbcTemplate) {
     }
 
     @Override
-    public int save(Long id, Long sessionId) {
+    public Long save(Long id, Long sessionId) {
         String sql = "insert into students (session_id, user_id, created_at) values (?, ?, ?)";
-        return jdbcTemplate.update(sql, sessionId, id, LocalDateTime.now());
+        KeyHolder keyHolder = new GeneratedKeyHolder();
+        jdbcTemplate.update(connection -> {
+            PreparedStatement ps = connection.prepareStatement(sql, new String[]{"id"});
+            ps.setLong(1, sessionId);
+            ps.setLong(2, id);
+            ps.setTimestamp(3, Timestamp.valueOf(LocalDateTime.now()));
+            return ps;
+        }, keyHolder);
+
+        return keyHolder.getKey().longValue();
     }
 
     @Override
     public Students findBySessionId(Long id) {
-        String sql = "select ns.id, ns.user_id, ns.password, ns.name, ns.email from students st inner join ns_user ns where st.user_id = ns.id and st.session_id = ?";
+        String sql = "select ns.id, ns.user_id, ns.password, ns.name, ns.email, ns.created_at, ns.updated_at from students st inner join ns_user ns where st.user_id = ns.id and st.session_id = ?";
         RowMapper<NsUser> rowMapper = (rs, rowNum) -> new NsUser(
                 rs.getLong(1),
                 rs.getString(2),
                 rs.getString(3),
                 rs.getString(4),
-                rs.getString(5)
+                rs.getString(5),
+                toLocalDateTime(rs.getTimestamp(6)),
+                toLocalDateTime(rs.getTimestamp(7))
         );
 
         return new Students(Set.of(jdbcTemplate.queryForObject(sql, rowMapper, id)));
     }
+
+    private LocalDateTime toLocalDateTime(Timestamp timestamp) {
+        if (timestamp == null) {
+            return null;
+        }
+        return timestamp.toLocalDateTime();
+    }
 }
diff --git a/src/main/java/nextstep/courses/repository/CoverImageRepository.java b/src/main/java/nextstep/courses/repository/CoverImageRepository.java
index 44948543c..7473f5c99 100644
--- a/src/main/java/nextstep/courses/repository/CoverImageRepository.java
+++ b/src/main/java/nextstep/courses/repository/CoverImageRepository.java
@@ -2,8 +2,12 @@
 
 import nextstep.courses.domain.CoverImage;
 
+import java.util.List;
+
 public interface CoverImageRepository {
-    int save(CoverImage coverImage);
+    int save(CoverImage coverImage, Long sessionId);
 
     CoverImage findById(Long id);
+
+    List<CoverImage> findAllBySessionId(Long id);
 }
diff --git a/src/main/java/nextstep/courses/repository/StudentsRepository.java b/src/main/java/nextstep/courses/repository/StudentsRepository.java
index c05268630..77d5edd63 100644
--- a/src/main/java/nextstep/courses/repository/StudentsRepository.java
+++ b/src/main/java/nextstep/courses/repository/StudentsRepository.java
@@ -4,7 +4,7 @@
 
 public interface StudentsRepository {
 
-    int save(Long id, Long sessionId);
+    Long save(Long id, Long sessionId);
 
     Students findBySessionId(Long id);
 }
diff --git a/src/main/java/nextstep/courses/service/CoverImageService.java b/src/main/java/nextstep/courses/service/CoverImageService.java
new file mode 100644
index 000000000..31488b613
--- /dev/null
+++ b/src/main/java/nextstep/courses/service/CoverImageService.java
@@ -0,0 +1,18 @@
+package nextstep.courses.service;
+
+import nextstep.courses.domain.CoverImage;
+import nextstep.courses.repository.CoverImageRepository;
+import org.springframework.transaction.annotation.Transactional;
+
+import javax.annotation.Resource;
+
+public class CoverImageService {
+
+    @Resource(name = "coverImageRepository")
+    private CoverImageRepository coverImageRepository;
+
+    @Transactional
+    public void createCoverImage(CoverImage image, Long sessionId) {
+        coverImageRepository.save(image, sessionId);
+    }
+}
diff --git a/src/main/java/nextstep/users/domain/NsUser.java b/src/main/java/nextstep/users/domain/NsUser.java
index 25050fee3..91c4d8289 100755
--- a/src/main/java/nextstep/users/domain/NsUser.java
+++ b/src/main/java/nextstep/users/domain/NsUser.java
@@ -124,14 +124,13 @@ public boolean isGuestUser() {
     public boolean equals(Object o) {
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
-        if (!super.equals(o)) return false;
         NsUser nsUser = (NsUser) o;
-        return Objects.equals(id, nsUser.id) && Objects.equals(userId, nsUser.userId) && Objects.equals(password, nsUser.password) && Objects.equals(name, nsUser.name) && Objects.equals(email, nsUser.email);
+        return id != null & Objects.equals(id, nsUser.id);
     }
 
     @Override
     public int hashCode() {
-        return Objects.hash(super.hashCode(), id, userId, password, name, email);
+        return id != null ? id.intValue() : 0;
     }
 
     @Override
diff --git a/src/main/resources/data.sql b/src/main/resources/data.sql
index 0d92f4161..118092d41 100644
--- a/src/main/resources/data.sql
+++ b/src/main/resources/data.sql
@@ -11,8 +11,9 @@ INSERT INTO question (id, writer_id, title, contents, created_at, deleted) VALUE
 
 INSERT INTO course (id, title, creator_id, created_at) VALUES (2, 'JPA 활용편1', 2, CURRENT_TIMESTAMP());
 
-INSERT INTO cover_image (id, size, extension, width, height, created_at) VALUES (2, 1, 'jpg', 300, 200, CURRENT_TIMESTAMP());
-
-INSERT INTO session (id, course_id, image_id, type, status, start_date, end_date, max_students, fee, created_at) VALUES (2, 2, 2, 'FREE', 'NOT_OPEN', '2023-12-01', '2023-12-31', 0, 0, CURRENT_TIMESTAMP());
-INSERT INTO session (id, course_id, image_id, type, status, start_date, end_date, max_students, fee, created_at) VALUES (3, 2, 2, 'PAID', 'NOT_OPEN', '2023-12-01', '2023-12-31', 30, 20000, CURRENT_TIMESTAMP());
+INSERT INTO cover_image (id, session_id, size, extension, width, height, created_at) VALUES (2, 3, 1, 'jpg', 300, 200, CURRENT_TIMESTAMP());
+INSERT INTO cover_image (id, session_id, size, extension, width, height, created_at) VALUES (3, 2, 1, 'jpg', 300, 200, CURRENT_TIMESTAMP());
+INSERT INTO cover_image (id, session_id, size, extension, width, height, created_at) VALUES (4, 2, 1, 'jpg', 300, 200, CURRENT_TIMESTAMP());
 
+INSERT INTO session (id, course_id, type, recruitment_status, start_date, end_date, max_students, fee, created_at) VALUES (2, 2, 'FREE', 'NOT_RECRUITMENT', '2023-12-01', '2023-12-31', 0, 0, CURRENT_TIMESTAMP());
+INSERT INTO session (id, course_id, type, recruitment_status, start_date, end_date, max_students, fee, created_at) VALUES (3, 2, 'PAID', 'NOT_RECRUITMENT', '2023-12-01', '2023-12-31', 30, 20000, CURRENT_TIMESTAMP());
diff --git a/src/main/resources/schema.sql b/src/main/resources/schema.sql
index 4e0d8e4fb..0b9580c0d 100644
--- a/src/main/resources/schema.sql
+++ b/src/main/resources/schema.sql
@@ -51,6 +51,7 @@ create table delete_history (
 
 create table cover_image (
     id bigint not null,
+    session_id bigint not null,
     size double not null,
     extension varchar(10) not null,
     width int not null,
@@ -63,9 +64,8 @@ create table cover_image (
 create table session (
     id bigint not null,
     course_id bigint not null,
-    image_id bigint not null,
     type varchar(10) not null,
-    status varchar(10) not null,
+    recruitment_status varchar(30) not null,
     start_date timestamp not null,
     end_date timestamp not null,
     max_students int,
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
index 24460c689..d6f5c34ed 100644
--- a/src/test/java/nextstep/courses/domain/CourseTest.java
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -4,6 +4,7 @@
 import org.junit.jupiter.api.Test;
 
 import java.time.LocalDate;
+import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -15,7 +16,7 @@ void add_session() {
         Course course = new Course(0L, "TDD, 클린 코드 with Java 17기", 1L);
         CoverImage coverImage = new CoverImage(1, "jpg", 300, 200);
         LocalDate now = LocalDate.now();
-        Session session = Session.ofFree(0L, 1L, coverImage, now, now);
+        Session session = Session.ofFree(0L, 1L, new CoverImages(List.of(coverImage)), now, now);
 
         course.addSession(session);
 
diff --git a/src/test/java/nextstep/courses/domain/SessionStatusTest.java b/src/test/java/nextstep/courses/domain/SessionStatusTest.java
new file mode 100644
index 000000000..f7909fb68
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionStatusTest.java
@@ -0,0 +1,24 @@
+package nextstep.courses.domain;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SessionStatusTest {
+
+    @Test
+    @DisplayName("오늘 날짜에 맞는 준비중, 진행중, 종료를 반환한다.")
+    void create() {
+        SessionStatus preparing = SessionStatus.of(LocalDate.now(), LocalDate.of(2023, 12, 15), LocalDate.of(2023, 12, 31));
+        assertThat(preparing).isEqualTo(SessionStatus.PREPARING);
+
+        SessionStatus inProgress = SessionStatus.of(LocalDate.now(), LocalDate.of(2023, 12, 1), LocalDate.of(2023, 12, 31));
+        assertThat(inProgress).isEqualTo(SessionStatus.IN_PROGRESS);
+
+        SessionStatus completed = SessionStatus.of(LocalDate.now(), LocalDate.of(2023, 12, 1), LocalDate.of(2023, 12, 5));
+        assertThat(completed).isEqualTo(SessionStatus.COMPLETED);
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
index f2b8fa35c..75a7637d3 100644
--- a/src/test/java/nextstep/courses/domain/SessionTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionTest.java
@@ -7,35 +7,36 @@
 import org.junit.jupiter.api.Test;
 
 import java.time.LocalDate;
+import java.util.List;
 
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.Assertions.*;
 
 class SessionTest {
 
     private static final LocalDate START_DATE = LocalDate.of(2023, 12, 1);
     private static final LocalDate END_DATE = LocalDate.of(2023, 12, 31);
 
-    @Test
-    @DisplayName("무료 강의 수강 신청 시 강의 상태가 모집중이 아니면 예외를 던진다.")
-    void register_status_check() {
-        Session freeSession = Session.ofFree(1L, 2L, coverImage(), START_DATE, END_DATE);
-        assertThatThrownBy(() -> freeSession.register(Payment.ofFree(1L, NsUserTest.JAVAJIGI)))
-                .isInstanceOf(NotOpenSessionException.class);
-    }
-
-    @Test
-    @DisplayName("강의 상태를 모집중으로 변경 시 현재 날짜가 강의 기간에 속하지 않으면 예외를 던진다.")
-    void register_open() {
-        Session session = Session.ofFree(1L, 2L, coverImage(), START_DATE, LocalDate.of(2023, 12, 2));
-        assertThatThrownBy(() -> session.openSession())
-                .isInstanceOf(OutOfSessionException.class);
-    }
+//    @Test
+//    @DisplayName("무료 강의 수강 신청 시 강의 상태가 모집중이 아니면 예외를 던진다.")
+//    void register_status_check() {
+//        Session freeSession = Session.ofFree(1L, 2L, coverImages(), START_DATE, END_DATE);
+//        assertThatThrownBy(() -> freeSession.register(Payment.ofFree(1L, NsUserTest.JAVAJIGI)))
+//                .isInstanceOf(NotOpenSessionException.class);
+//    }
+
+//    @Test
+//    @DisplayName("강의 상태를 모집중으로 변경 시 현재 날짜가 강의 기간에 속하지 않으면 예외를 던진다.")
+//    void register_open() {
+//        Session session = Session.ofFree(1L, 2L, coverImages(), START_DATE, LocalDate.of(2023, 12, 2));
+//        assertThatThrownBy(() -> session.startRecruiting())
+//                .isInstanceOf(OutOfSessionException.class);
+//    }
 
     @Test
     @DisplayName("유료 강의 수강 신청 시 최대 수강 인원을 초과하면 예외를 던진다.")
     void register_over_students() {
-        Session paidSession = Session.ofPaid(1L, 2L, coverImage(), START_DATE, END_DATE, 1, 10_000L);
-        paidSession.openSession();
+        Session paidSession = Session.ofPaid(1L, 2L, coverImages(), START_DATE, END_DATE, 1, 10_000L);
+        paidSession.startRecruiting();
 
         paidSession.register(Payment.ofPaid(1L, 1L, NsUserTest.JAVAJIGI, 10_000L));
 
@@ -46,8 +47,8 @@ void register_over_students() {
     @Test
     @DisplayName("유료 강의 수강 신청 시 결제금액과 수강료가 일치하는지 확인하지 않으면 예외를 던진다.")
     void session_fee_test() {
-        Session paidSession = Session.ofPaid(1L, 2L, coverImage(), START_DATE, END_DATE, 1, 10_000L);
-        paidSession.openSession();
+        Session paidSession = Session.ofPaid(1L, 2L, coverImages(), START_DATE, END_DATE, 1, 10_000L);
+        paidSession.startRecruiting();
 
         assertThatThrownBy(() -> paidSession.register(Payment.ofPaid(2L, 1L, NsUserTest.SANJIGI, 8_000L)))
                 .isInstanceOf(PaymentMismatchException.class);
@@ -56,15 +57,15 @@ void session_fee_test() {
     @Test
     @DisplayName("강의 생성 시 결제금액과 수강료가 음수면 예외를 던진다.")
     void session_paid_condition_null() {
-        assertThatThrownBy(() -> Session.ofPaid(1L, 2L, coverImage(), START_DATE, END_DATE, -1, -1L))
+        assertThatThrownBy(() -> Session.ofPaid(1L, 2L, coverImages(), START_DATE, END_DATE, -1, -1L))
                 .isInstanceOf(NegativePaidConditionException.class);
     }
 
     @Test
     @DisplayName("중복 수강 신청 시 예외를 던진다.")
     void duplicate_register() {
-        Session paidSession = Session.ofPaid(1L, 2L, coverImage(), START_DATE, END_DATE, 2, 10_000L);
-        paidSession.openSession();
+        Session paidSession = Session.ofPaid(1L, 2L, coverImages(), START_DATE, END_DATE, 2, 10_000L);
+        paidSession.startRecruiting();
 
         paidSession.register(Payment.ofPaid(1L, 1L, NsUserTest.SANJIGI, 10_000L));
 
@@ -72,7 +73,30 @@ void duplicate_register() {
                 .isInstanceOf(DuplicateStudentsException.class);
     }
 
-    private static CoverImage coverImage() {
-        return new CoverImage(1, "gif", 300, 200);
+    @Test
+    @DisplayName("강의 생성 시 이미지가 없으면 예외를 던진다.")
+    void empty_images() {
+        assertThatThrownBy(() -> Session.ofPaid(1L, 2L, new CoverImages(null), START_DATE, END_DATE, 1, 10_000L))
+                .isInstanceOf(EmptyCoverImageException.class);
+    }
+
+    @Test
+    @DisplayName("강의 생성 시 기간 내면 상태가 준비중이고 모집 전이다.")
+    void session_status() {
+        Session session = Session.ofPaid(1L, 2L, coverImages(), START_DATE, END_DATE, 1, 10_000L);
+        assertThat(session.sessionStatus()).isEqualTo(SessionStatus.IN_PROGRESS.name());
+        assertThat(session.recruitmentStatus()).isEqualTo(RecruitmentStatus.NOT_RECRUITMENT.name());
+    }
+
+    @Test
+    @DisplayName("강의 상태가 모집중이 아니어도 진행 중이면 수강신청이 가능하다.")
+    void can_register_not_recruitment() {
+        Session freeSession = Session.ofFree(1L, 2L, coverImages(), START_DATE, END_DATE);
+        assertThatCode(() -> freeSession.register(Payment.ofFree(1L, NsUserTest.JAVAJIGI)))
+                .doesNotThrowAnyException();
+    }
+
+    private static CoverImages coverImages() {
+        return new CoverImages(List.of(new CoverImage(1, "gif", 300, 200)));
     }
 }
diff --git a/src/test/java/nextstep/courses/infrastructure/CoverImageRepositoryTest.java b/src/test/java/nextstep/courses/infrastructure/CoverImageRepositoryTest.java
index c3d3e8cac..4589f3f51 100644
--- a/src/test/java/nextstep/courses/infrastructure/CoverImageRepositoryTest.java
+++ b/src/test/java/nextstep/courses/infrastructure/CoverImageRepositoryTest.java
@@ -10,6 +10,8 @@
 import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest;
 import org.springframework.jdbc.core.JdbcTemplate;
 
+import java.util.List;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 @JdbcTest
@@ -30,7 +32,7 @@ void setUp() {
     @Test
     void crud() {
         CoverImage image = new CoverImage(1, "jpg", 300, 200);
-        int count = coverImageRepository.save(image);
+        int count = coverImageRepository.save(image, 2L);
         assertThat(count).isEqualTo(1);
         CoverImage savedImage = coverImageRepository.findById(1L);
         assertThat(savedImage.getId()).isEqualTo(image.getId());
@@ -41,4 +43,11 @@ void crud() {
     void find() {
         assertThat(coverImageRepository.findById(2L).getId()).isEqualTo(2L);
     }
+
+    @Test
+    void findAllBySessionId() {
+        List<CoverImage> images = coverImageRepository.findAllBySessionId(2L);
+        assertThat(images.get(0).getId()).isEqualTo(3L);
+        assertThat(images.get(1).getId()).isEqualTo(4L);
+    }
 }
diff --git a/src/test/java/nextstep/courses/infrastructure/SessionRepositoryTest.java b/src/test/java/nextstep/courses/infrastructure/SessionRepositoryTest.java
index 9372e44ad..18fd14828 100644
--- a/src/test/java/nextstep/courses/infrastructure/SessionRepositoryTest.java
+++ b/src/test/java/nextstep/courses/infrastructure/SessionRepositoryTest.java
@@ -1,8 +1,8 @@
 package nextstep.courses.infrastructure;
 
 import nextstep.courses.domain.CoverImage;
+import nextstep.courses.domain.CoverImages;
 import nextstep.courses.domain.Session;
-import nextstep.courses.repository.CoverImageRepository;
 import nextstep.courses.repository.SessionRepository;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -13,6 +13,7 @@
 import org.springframework.jdbc.core.JdbcOperations;
 
 import java.time.LocalDate;
+import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertAll;
@@ -26,17 +27,15 @@ class SessionRepositoryTest {
     private JdbcOperations jdbcTemplates;
 
     private SessionRepository sessionRepository;
-    private CoverImageRepository coverImageRepository;
 
     @BeforeEach
     void setUp() {
         sessionRepository = new JdbcSessionRepository(jdbcTemplates);
-        coverImageRepository = new JdbcCoverImageRepository(jdbcTemplates);
     }
 
     @Test
     void free_crud() {
-        Session session = Session.ofFree(1L, 2L, coverImage(), LocalDate.now(), LocalDate.of(2023, 12, 31));
+        Session session = Session.ofFree(1L, 2L, coverImages(), LocalDate.now(), LocalDate.of(2023, 12, 31));
         int count = sessionRepository.save(session);
         assertThat(count).isEqualTo(1);
 
@@ -47,7 +46,7 @@ void free_crud() {
 
     @Test
     void paid_crud() {
-        Session session = Session.ofPaid(1L, 2L, coverImage(), LocalDate.now(), LocalDate.of(2023, 12, 31), 10, 10_000L);
+        Session session = Session.ofPaid(1L, 2L, coverImages(), LocalDate.now(), LocalDate.of(2023, 12, 31), 10, 10_000L);
         int count = sessionRepository.save(session);
         assertThat(count).isEqualTo(1);
 
@@ -60,7 +59,7 @@ void paid_crud() {
         LOGGER.debug("Session: {}", paidSession);
     }
 
-    private CoverImage coverImage() {
-        return coverImageRepository.findById(2L);
+    private CoverImages coverImages() {
+        return new CoverImages(List.of(new CoverImage(1, "jpg", 300, 200)));
     }
 }
diff --git a/src/test/java/nextstep/courses/infrastructure/StudentsRepositoryTest.java b/src/test/java/nextstep/courses/infrastructure/StudentsRepositoryTest.java
index ccd17d206..db57a6084 100644
--- a/src/test/java/nextstep/courses/infrastructure/StudentsRepositoryTest.java
+++ b/src/test/java/nextstep/courses/infrastructure/StudentsRepositoryTest.java
@@ -37,15 +37,14 @@ void setUp() {
     void crud() {
         NsUser nsUser = new NsUser(1L, "javajigi", "test", "자바지기", "javajigi@slipp.net");
         Session session = sessionRepository.findById(3L);
-        session.openSession();
+        session.startRecruiting();
 
-        session.register(Payment.ofPaid(1L, 1L, nsUser, 20_000L));
-        int count = studentsRepository.save(nsUser.getId(), 2L);
-        assertThat(count).isEqualTo(1);
+        session.register(Payment.ofPaid(1L, 3L, nsUser, 20_000L));
+        Long id = studentsRepository.save(nsUser.getId(), 3L);
+        assertThat(id).isEqualTo(1L);
 
-        Students students = studentsRepository.findBySessionId(2L);
-        System.out.println(students);
-        assertThat(students.isContains(nsUser)).isTrue(); //왜 false인지 모르겠음 ㅠㅠ
+        Students students = studentsRepository.findBySessionId(3L);
+        assertThat(students.isContains(nsUser)).isTrue();
         LOGGER.debug("Students: {}", students);
     }
 }