diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index d843f34..35eb1dd 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="VcsDirectoryMappings" defaultProject="true" />
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
 </project>
\ No newline at end of file
diff --git a/src/main/java/org/sopt/seminar1/Diary.java b/src/main/java/org/sopt/seminar1/Diary.java
new file mode 100644
index 0000000..c56b161
--- /dev/null
+++ b/src/main/java/org/sopt/seminar1/Diary.java
@@ -0,0 +1,38 @@
+package org.sopt.seminar1;
+
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+
+public class Diary {
+    private Long id;
+    private final String body;
+    private boolean isDeleted = false;
+    private LocalDateTime lastEditedDateTime;
+
+    public Diary(Long id, String body) {
+        this.id = id;
+        this.body = body;
+        this.lastEditedDateTime = LocalDateTime.now();
+    }
+
+    public Long getId() {
+        return id;
+    }
+    public String getBody() {
+        return body;
+    }
+
+    public boolean isDeleted() {
+        return isDeleted;
+    }
+    public void setDeleted(boolean deleted) {
+        this.isDeleted = deleted;
+    }
+
+    public LocalDateTime getLastEditedDateTime() {
+        return lastEditedDateTime;
+    }
+    public void setLastEditedDateTime(LocalDateTime lastEditedDateTime) {
+        this.lastEditedDateTime = lastEditedDateTime;
+    }
+}
diff --git a/src/main/java/org/sopt/seminar1/DiaryController.java b/src/main/java/org/sopt/seminar1/DiaryController.java
new file mode 100644
index 0000000..a1b71cf
--- /dev/null
+++ b/src/main/java/org/sopt/seminar1/DiaryController.java
@@ -0,0 +1,63 @@
+package org.sopt.seminar1;
+
+import java.util.List;
+
+public class DiaryController {
+    private Status status = Status.READY;
+    private final DiaryService diaryService = new DiaryService();
+
+    Status getStatus() {
+        return status;
+    }
+
+    void boot() {
+        this.status = Status.RUNNING;
+    }
+
+    void finish() {
+        this.status = Status.FINISHED;
+    }
+
+    // APIS
+    final List<Diary> getList() {
+        return diaryService.getDiaryList();
+    }
+
+    final void post(final String body) {
+        diaryService.writeDiary(body);
+    }
+
+    final void delete(final String id) {
+        long longId = validateAndConvertId(id);
+        diaryService.deleteDiary(longId);
+    }
+
+    final void patch(final String id, final String body) {
+        long longId = validateAndConvertId(id);
+        diaryService.updateDiary(longId, body);
+    }
+
+    final void restore(final String id) {
+        long longId = validateAndConvertId(id);
+        diaryService.restoreDiary(longId);
+    }
+
+    enum Status {
+        READY,
+        RUNNING,
+        FINISHED,
+        ERROR,
+    }
+
+    private long validateAndConvertId(final String id) {
+        if (!id.matches("^[1-9][0-9]*$")) {
+            throw new Main.UI.InvalidInputException();
+        }
+
+        try {
+            return Long.parseLong(id);
+        } catch (NumberFormatException e) {
+            throw new IllegalArgumentException("유효한 long 형식의 ID여야 합니다.");
+        }
+    }
+}
diff --git a/src/main/java/org/sopt/seminar1/DiaryRepository.java b/src/main/java/org/sopt/seminar1/DiaryRepository.java
new file mode 100644
index 0000000..6cd51c7
--- /dev/null
+++ b/src/main/java/org/sopt/seminar1/DiaryRepository.java
@@ -0,0 +1,67 @@
+package org.sopt.seminar1;
+
+import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicLong;
+
+public class DiaryRepository {
+    private final Map<Long, Diary> storage = new ConcurrentHashMap<>();
+    private final AtomicLong numbering = new AtomicLong();
+    private int updateCount = 0;
+
+    void save(Diary diary) {
+        final long id = numbering.addAndGet(1);
+        diary.setDeleted(false);
+        diary = new Diary(id, diary.getBody());
+        storage.put(id, diary); // Diary 객체를 저장
+    }
+
+    List<Diary> findAll() {
+        final List<Diary> diaryList = new ArrayList<>();
+        for (long index = 1; index <= numbering.longValue(); index++) {
+            final Diary diary = storage.get(index);
+            if (diary != null && !diary.isDeleted()) {
+                diaryList.add(diary);
+            }
+        }
+        return diaryList;
+    }
+
+    void delete(final long id) {
+        Diary diary = storage.get(id);
+        if (diary != null) {
+            diary.setDeleted(true);
+        }
+    }
+
+    void update(final long id, final String newBody) {
+        Diary diary = storage.get(id);
+        if (diary != null && !diary.isDeleted()) {
+            LocalDateTime now = LocalDateTime.now();
+            LocalDateTime lastEditedDateTime = diary.getLastEditedDateTime();
+
+            if (!(lastEditedDateTime.toLocalDate().equals(now.toLocalDate()))) {
+                updateCount = 0;
+                diary.setLastEditedDateTime(now);
+            }
+
+            if (updateCount <2){
+                updateCount++;
+                diary.setDeleted(false);
+                storage.replace(id, new Diary(id, newBody));
+            } else {
+                throw new Main.UI.InvalidInputException();
+            }
+        }
+    }
+
+    void restore(final long id) {
+        Diary diary = storage.get(id);
+        if (diary != null && diary.isDeleted()) {
+            diary.setDeleted(false);
+        }
+    }
+}
diff --git a/src/main/java/org/sopt/seminar1/DiaryService.java b/src/main/java/org/sopt/seminar1/DiaryService.java
new file mode 100644
index 0000000..b95e646
--- /dev/null
+++ b/src/main/java/org/sopt/seminar1/DiaryService.java
@@ -0,0 +1,24 @@
+package org.sopt.seminar1;
+
+import java.util.List;
+
+public class DiaryService {
+    private final DiaryRepository diaryRepository = new DiaryRepository();
+
+    void writeDiary(String body){
+        final Diary diary = new Diary(null, body);
+        diaryRepository.save(diary);
+    }
+    List<Diary> getDiaryList(){
+        return diaryRepository.findAll();
+    }
+    void deleteDiary(long id){
+        diaryRepository.delete(id);
+    }
+    void updateDiary(long id, String body){
+        diaryRepository.update(id ,body);
+    }
+    void restoreDiary(long id) { // 복구 기능 추가
+        diaryRepository.restore(id);
+    }
+}
diff --git a/src/main/java/org/sopt/seminar1/Main.java b/src/main/java/org/sopt/seminar1/Main.java
new file mode 100644
index 0000000..b49025b
--- /dev/null
+++ b/src/main/java/org/sopt/seminar1/Main.java
@@ -0,0 +1,188 @@
+package org.sopt.seminar1;
+
+import java.io.*;
+
+public class Main {
+    public static void main(String[] args) {
+        final UI ui;
+        try {
+            ui = new DiaryUI(new DiaryController());
+            ui.runRepeatedly();
+        } catch (Throwable t) {
+
+        }
+    }
+
+    interface UI {
+        void runRepeatedly() throws IOException;
+
+        class UIException extends RuntimeException {
+        }
+
+        class InvalidInputException extends UIException {
+        }
+    }
+
+    static class DiaryUI implements UI {
+        private final DiaryController server;
+        private String selected;
+
+        public DiaryUI(DiaryController server) throws IOException {
+            this.server = server;
+            server.boot();
+            ConsoleIO.printLine(getStartMessage());
+        }
+
+        public void runRepeatedly() throws IOException {
+
+            do {
+                if (onMenu()) {
+                    ConsoleIO.printLine("");
+                    ConsoleIO.printLine(getMenu());
+                    selected = ConsoleIO.readLine().trim().toUpperCase();
+                }
+
+                try {
+                    run();
+                } catch (InvalidInputException e) {
+                    ConsoleIO.printLine("잘못된 값을 입력하였습니다.");
+                }
+
+                if (isFinished()) {
+                    ConsoleIO.printLine(getFinishMessage());
+                    break;
+                }
+
+                selected = null;
+            } while (isRunning());
+        }
+
+        //30글자 제한
+        private void validateInputLength(final String input) throws InvalidInputException, IOException {
+            if (input.length() > 30) {
+                ConsoleIO.printLine("일기는 최대 30글자까지만 입력할 수 있습니다. 다시 입력해주세요.");
+                throw new InvalidInputException();
+            }
+        }
+
+        private void run() throws IOException {
+            switch (server.getStatus()) {
+                case READY, FINISHED, ERROR -> throw new UIException();
+
+                case RUNNING -> {
+                    switch (selected) {
+                        case "GET" -> {
+                            server.getList().forEach(diary -> {
+                                try {
+                                    ConsoleIO.printLine(diary.getId()+" : "+diary.getBody());
+                                } catch (IOException e) {
+                                    throw new RuntimeException(e);
+                                }
+                            });
+                        }
+                        case "POST" -> {
+                            ConsoleIO.printLine("한 줄 일기를 작성해주세요!");
+                            final String input = ConsoleIO.readLine();
+                            validateInputLength(input);
+                            server.post(input);
+                        }
+
+                        case "DELETE" -> {
+                            ConsoleIO.printLine("삭제할 id 를 입력하세요!");
+                            final String input = ConsoleIO.readLine();
+                            server.delete(input);
+                        }
+                        case "PATCH" -> {
+                            ConsoleIO.printLine("수정할 id 를 입력하세요!");
+                            final String inputId = ConsoleIO.readLine();
+
+                            ConsoleIO.printLine("수정 body 를 입력하세요!");
+                            final String inputBody = ConsoleIO.readLine();
+                            validateInputLength(inputBody);
+                            server.patch(inputId, inputBody);
+                        }
+                        case "RESTORE" -> {
+                            ConsoleIO.printLine("복구할 id 를 입력하세요!");
+                            final String input = ConsoleIO.readLine();
+                            server.restore(input); // 복구 기능 호출
+                        }
+                        case "FINISH" -> {
+                            server.finish();
+                        }
+                        default -> {
+                            throw new InvalidInputException();
+                        }
+                    }
+                }
+
+            }
+        }
+
+        private boolean isRunning() {
+            return server.getStatus() == DiaryController.Status.RUNNING;
+        }
+
+        private boolean isFinished() {
+            return server.getStatus() == DiaryController.Status.FINISHED;
+        }
+
+        private boolean onMenu() {
+            return selected == null;
+        }
+
+        private String getMenu() {
+            return """
+                    ============================
+                    - GET : 일기 불러오기
+                    - POST : 일기 작성하기
+                    - DELETE : 일기 제거하기
+                    - PATCH : 일기 수정하기
+                    - RESTORE : 일기 복구하기
+                    """;
+
+        }
+
+        private String getStartMessage() {
+            return "시작합니다 :)";
+        }
+
+        private String getFinishMessage() {
+            return "종료됩니다 :)";
+        }
+    }
+
+    // not thread safe
+    private static class ConsoleIO {
+        private final static BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(System.out));
+        private final static BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
+        private final static StringBuilder sb = new StringBuilder();
+
+        public static void printLine(final String toPrint) throws IOException {
+            if (toPrint == null) {
+                throw new IllegalArgumentException("console can not print null");
+            }
+
+            appendLine(toPrint);
+            print();
+            clearStringBuilder();
+        }
+
+        public static String readLine() throws IOException {
+            return bufferedReader.readLine();
+        }
+
+        private static void appendLine(final String toPrint) {
+            sb.append(toPrint);
+            sb.append("\n");
+        }
+
+        private static void print() throws IOException {
+            bufferedWriter.write(sb.toString());
+            bufferedWriter.flush();
+        }
+
+        private static void clearStringBuilder() {
+            sb.setLength(0);
+        }
+    }
+}