diff --git a/Localization/Locale/en.json b/Localization/Locale/en.json
new file mode 100644
index 0000000..f6a667e
--- /dev/null
+++ b/Localization/Locale/en.json
@@ -0,0 +1,85 @@
+{
+  "ui.button.presets": "Presets",
+  "ui.placeholder.render_fps": "Render FPS",
+  "ui.placeholder.video_fps": "Video FPS",
+  "ui.placeholder.render_width": "Render Width (px)",
+  "ui.placeholder.render_height": "Render Height (px)",
+  "ui.button.video_config": "Video Encoding Config",
+  "ui.button.audio_config": "Audio Encoding Config",
+  "ui.placeholder.delay_after_end": "Delay After Level End",
+  "ui.toggle.show_judgement": "Show Judgement",
+  "ui.button.go_render": "Go Render",
+  "ui.button.advanced_settings": "Advanced Settings...",
+  "ui.version.expired": " (Expired)",
+  "ui.validation.required_fields": "Required input fields are empty or invalid. Please fill in all settings.",
+
+  "ui.advanced.title": "Advanced Settings",
+  "ui.advanced.file_extension": "File Extension",
+  "ui.advanced.process_audio": "Process Audio",
+  "ui.advanced.non_tile_mode": "Non-Tile Mode",
+  "ui.advanced.random_seed": "Random Seed (Optional)",
+  "ui.button.cancel": "Cancel",
+  "ui.button.save": "Save",
+
+  "ui.video.title": "Video Encoding Settings",
+  "ui.video.codec": "Codec",
+  "ui.video.rate_control": "Bitrate Control Mode",
+  "ui.video.bitrate": "Bitrate (kbps)",
+  "ui.video.max_bitrate": "Max Bitrate (kbps)",
+  "ui.video.qp": "Quality (QP)",
+  "ui.video.keyframe_interval": "Keyframe Interval (s)",
+  "ui.video.force_software": "Force Software Encoder",
+  "ui.video.qp_zero_warning": "Warning: Setting QP to 0 applies lossless encoding and may result in very large file sizes.",
+
+  "ui.audio.title": "Audio Encoding Settings",
+  "ui.audio.rendering": "Audio Rendering",
+  "ui.audio.sample_rate": "Sample Rate (Hz)",
+  "ui.audio.channels": "Audio Channels",
+  "ui.audio.channels_mono": "1 (Mono)",
+  "ui.audio.channels_stereo": "2 (Stereo)",
+  "ui.audio.bitrate": "Audio Bitrate (kbps)",
+
+  "ui.preset.title": "Preset Settings",
+  "ui.preset.new_name": "New Preset Name",
+  "ui.preset.no_presets": "No saved presets.",
+  "ui.button.load": "Load",
+  "ui.button.delete": "Delete",
+  "ui.button.close": "Close",
+  "ui.preset.save_failed": "Save Failed",
+  "ui.preset.enter_name": "Please enter a preset name.",
+  "ui.preset.invalid_inputs": "Cannot save preset because required input values are empty or invalid.",
+  "ui.preset.save_error": "An error occurred while saving the preset: {0}",
+  "ui.preset.delete_title": "Delete Preset",
+  "ui.preset.delete_confirm": "Are you sure you want to delete the preset '{0}'?",
+  "ui.button.yes": "Yes",
+  "ui.button.no": "No",
+  "ui.button.ok": "OK",
+
+  "ui.ffmpeg.title": "FFmpeg Library Installation Required",
+  "ui.ffmpeg.desc_main": "FFmpeg shared libraries are required to render video.",
+  "ui.ffmpeg.desc_osx": "For macOS, reliable public builds are unavailable, so FFmpeg 8.1 must be built manually.\nClick the button below to open the official FFmpeg website.",
+  "ui.ffmpeg.desc_auto": "Click the button below to automatically download and install from the internet.\n<color=#aaaaaa><size=13>(Download size: ~70MB, extracted to UserLibs folder)</size></color>",
+  "ui.ffmpeg.button_download": "Download & Install",
+  "ui.ffmpeg.button_open_web": "Open Download Page",
+  "ui.ffmpeg.button_cancel": "Cancel",
+  "ui.ffmpeg.button_opening": "Opening...",
+  "ui.ffmpeg.status_downloading": "Downloading... ({0:F1}%)",
+  "ui.ffmpeg.status_extracting": "Extracting FFmpeg files...",
+  "ui.ffmpeg.status_done": "Done! Restarting audio/video engine...",
+  "ui.ffmpeg.status_failed": "Failed to download FFmpeg: {0}",
+
+  "ui.escape.cancelling": "<color=#FF5252>Cancelling in {0:F1}s..</color>\n<size=40><color=#DDDDDD>Hold Esc to cancel render</color></size>",
+
+  "ui.monitor.title": "ADOFAI Renderer Realtime Monitor",
+  "ui.monitor.queue": "• Queue: <b>{0}</b> / {1} frames",
+  "ui.monitor.rendered_frames": "• Rendered Frames: <b>{0}</b>",
+  "ui.monitor.frames_sent": "• Frames Sent: <b>{0}</b>",
+  "ui.monitor.throttling": "• Throttling Controls: {0} times",
+  "ui.monitor.readback_failures": "• Readback Hard Failures: <color=#ff3333>{0}</color> times",
+  "ui.monitor.skip_retry": "• Render Skip-Retry: {0} / {1}",
+  "ui.monitor.memory": "• Mono Heap Memory: {0:F2} MB",
+
+  "ui.notification.complete_title": "Rendering Complete!",
+  "ui.notification.complete_msg": "{0} saved successfully.",
+  "ui.notification.video_fallback": "Video"
+}
diff --git a/Localization/Locale/ko.json b/Localization/Locale/ko.json
new file mode 100644
index 0000000..ecc7747
--- /dev/null
+++ b/Localization/Locale/ko.json
@@ -0,0 +1,85 @@
+{
+  "ui.button.presets": "프리셋",
+  "ui.placeholder.render_fps": "렌더링 FPS",
+  "ui.placeholder.video_fps": "영상 FPS",
+  "ui.placeholder.render_width": "렌더링 너비 (px)",
+  "ui.placeholder.render_height": "렌더링 높이 (px)",
+  "ui.button.video_config": "비디오 인코딩 설정",
+  "ui.button.audio_config": "오디오 인코딩 설정",
+  "ui.placeholder.delay_after_end": "레벨 종료 후 대기 시간 (초)",
+  "ui.toggle.show_judgement": "판정 텍스트 표시",
+  "ui.button.go_render": "렌더링 시작",
+  "ui.button.advanced_settings": "고급 설정...",
+  "ui.version.expired": " (만료됨)",
+  "ui.validation.required_fields": "필수 입력란이 비어 있거나 올바르지 않습니다. 모든 설정을 확인해 주세요.",
+
+  "ui.advanced.title": "고급 설정",
+  "ui.advanced.file_extension": "파일 확장자",
+  "ui.advanced.process_audio": "오디오 처리",
+  "ui.advanced.non_tile_mode": "논타일 모드",
+  "ui.advanced.random_seed": "랜덤 시드 (선택 사항)",
+  "ui.button.cancel": "취소",
+  "ui.button.save": "저장",
+
+  "ui.video.title": "비디오 인코딩 설정",
+  "ui.video.codec": "코덱",
+  "ui.video.rate_control": "비트레이트 제어 모드",
+  "ui.video.bitrate": "비트레이트 (kbps)",
+  "ui.video.max_bitrate": "최대 비트레이트 (kbps)",
+  "ui.video.qp": "품질 (QP)",
+  "ui.video.keyframe_interval": "키프레임 간격 (초)",
+  "ui.video.force_software": "강제 소프트웨어 인코더",
+  "ui.video.qp_zero_warning": "경고: QP를 0으로 설정하면 무손실 인코딩이 적용되어 파일 크기가 매우 커질 수 있습니다.",
+
+  "ui.audio.title": "오디오 인코딩 설정",
+  "ui.audio.rendering": "오디오 렌더링",
+  "ui.audio.sample_rate": "샘플레이트 (Hz)",
+  "ui.audio.channels": "오디오 채널",
+  "ui.audio.channels_mono": "1 (모노)",
+  "ui.audio.channels_stereo": "2 (스테레오)",
+  "ui.audio.bitrate": "오디오 비트레이트 (kbps)",
+
+  "ui.preset.title": "프리셋 설정",
+  "ui.preset.new_name": "새 프리셋 이름",
+  "ui.preset.no_presets": "저장된 프리셋이 없습니다.",
+  "ui.button.load": "불러오기",
+  "ui.button.delete": "삭제",
+  "ui.button.close": "닫기",
+  "ui.preset.save_failed": "저장 실패",
+  "ui.preset.enter_name": "프리셋 이름을 입력해 주세요.",
+  "ui.preset.invalid_inputs": "필수 입력값이 비어 있거나 올바르지 않아 프리셋을 저장할 수 없습니다.",
+  "ui.preset.save_error": "프리셋 저장 중 오류가 발생했습니다: {0}",
+  "ui.preset.delete_title": "프리셋 삭제",
+  "ui.preset.delete_confirm": "정말 '{0}' 프리셋을 삭제하시겠습니까?",
+  "ui.button.yes": "예",
+  "ui.button.no": "아니오",
+  "ui.button.ok": "확인",
+
+  "ui.ffmpeg.title": "FFmpeg 라이브러리 설치 필요",
+  "ui.ffmpeg.desc_main": "영상을 렌더링하려면 FFmpeg 공유 라이브러리가 필요합니다.",
+  "ui.ffmpeg.desc_osx": "macOS의 경우 신뢰할 수 있는 빌드가 제공되지 않아 FFmpeg 8.1을 직접 빌드해야 합니다.\n아래 버튼을 눌러 공식 FFmpeg 웹사이트를 방문하세요.",
+  "ui.ffmpeg.desc_auto": "아래 버튼을 눌러 인터넷에서 자동으로 다운로드하여 설치합니다.\n<color=#aaaaaa><size=13>(다운로드 크기: 약 70MB, UserLibs 폴더에 압축 해제됨)</size></color>",
+  "ui.ffmpeg.button_download": "다운로드 및 설치",
+  "ui.ffmpeg.button_open_web": "다운로드 페이지 열기",
+  "ui.ffmpeg.button_cancel": "취소",
+  "ui.ffmpeg.button_opening": "열리는 중...",
+  "ui.ffmpeg.status_downloading": "다운로드 중... ({0:F1}%)",
+  "ui.ffmpeg.status_extracting": "FFmpeg 파일 압축 해제 중...",
+  "ui.ffmpeg.status_done": "완료! 오디오/비디오 엔진을 재시작합니다...",
+  "ui.ffmpeg.status_failed": "FFmpeg 다운로드 실패: {0}",
+
+  "ui.escape.cancelling": "<color=#FF5252>{0:F1}초 후 취소됩니다..</color>\n<size=40><color=#DDDDDD>렌더링을 취소하려면 Esc를 길게 누르세요</color></size>",
+
+  "ui.monitor.title": "ADOFAI Renderer 실시간 모니터",
+  "ui.monitor.queue": "• 대기열: <b>{0}</b> / {1} 프레임",
+  "ui.monitor.rendered_frames": "• 렌더링된 프레임: <b>{0}</b>",
+  "ui.monitor.frames_sent": "• 전송된 프레임: <b>{0}</b>",
+  "ui.monitor.throttling": "• 쓰로틀링 제어: {0}회",
+  "ui.monitor.readback_failures": "• 리드백 실패: <color=#ff3333>{0}</color>회",
+  "ui.monitor.skip_retry": "• 렌더 건너뜀-재시도: {0} / {1}",
+  "ui.monitor.memory": "• 모노 힙 메모리: {0:F2} MB",
+
+  "ui.notification.complete_title": "렌더링 완료!",
+  "ui.notification.complete_msg": "{0}이(가) 성공적으로 저장되었습니다.",
+  "ui.notification.video_fallback": "동영상"
+}
diff --git a/Localization/LocalizationManager.cs b/Localization/LocalizationManager.cs
new file mode 100644
index 0000000..181f77b
--- /dev/null
+++ b/Localization/LocalizationManager.cs
@@ -0,0 +1,241 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using MelonLoader;
+using Newtonsoft.Json;
+using UnityEngine;
+
+namespace ADOFAIRenderer.Localization;
+
+/// <summary>
+/// Provides access to localized strings and handles language synchronization with the game.
+/// </summary>
+internal static class LocalizationManager
+{
+    private static readonly Dictionary<string, Dictionary<string, string>> Locales = new(StringComparer.OrdinalIgnoreCase);
+    private static readonly string FallbackLocaleCode = "en";
+
+    /// <summary>
+    /// Event triggered when the active language changes.
+    /// </summary>
+    public static event Action<SystemLanguage>? OnLanguageChanged;
+
+    /// <summary>
+    /// Currently active SystemLanguage.
+    /// </summary>
+    public static SystemLanguage CurrentLanguage { get; private set; } = SystemLanguage.English;
+
+    /// <summary>
+    /// Currently active locale code (e.g. "en", "ko").
+    /// </summary>
+    public static string CurrentLocaleCode { get; private set; } = "en";
+
+    private static bool _initialized;
+
+    /// <summary>
+    /// Initializes the localization system and loads embedded language dictionaries.
+    /// </summary>
+    public static void Initialize()
+    {
+        if (_initialized) return;
+        _initialized = true;
+
+        LoadEmbeddedLocales();
+
+        // Detect initial language from game settings
+        var initialLang = DetectGameLanguage();
+        SetLanguage(initialLang, notify: false);
+
+        LogMsg($"[Localization] Initialized. Active language: {CurrentLanguage} ({CurrentLocaleCode})");
+    }
+
+    private static void LogMsg(string msg)
+    {
+        try { Melon<RenderMod>.Logger.Msg(msg); }
+        catch { Console.WriteLine(msg); }
+    }
+
+    private static void LogError(string msg)
+    {
+        try { Melon<RenderMod>.Logger.Error(msg); }
+        catch { Console.Error.WriteLine(msg); }
+    }
+
+    /// <summary>
+    /// Loads all *.json locale files embedded in this assembly.
+    /// </summary>
+    private static void LoadEmbeddedLocales()
+    {
+        var assembly = typeof(LocalizationManager).Assembly;
+        var resourceNames = assembly.GetManifestResourceNames();
+
+        foreach (var resourceName in resourceNames)
+        {
+            if (!resourceName.EndsWith(".json", StringComparison.OrdinalIgnoreCase)) continue;
+            if (!resourceName.Contains("Localization.Locale")) continue;
+
+            try
+            {
+                using var stream = assembly.GetManifestResourceStream(resourceName);
+                if (stream == null) continue;
+
+                using var reader = new StreamReader(stream);
+                var json = reader.ReadToEnd();
+                var dict = JsonConvert.DeserializeObject<Dictionary<string, string>>(json);
+
+                if (dict != null)
+                {
+                    // Extract locale code from resource name: e.g. "ADOFAIRenderer.Localization.Locale.ko.json" -> "ko"
+                    var parts = resourceName.Split('.');
+                    if (parts.Length >= 2)
+                    {
+                        var code = parts[^2].ToLowerInvariant();
+                        Locales[code] = dict;
+                        LogMsg($"[Localization] Loaded locale '{code}' ({dict.Count} keys).");
+                    }
+                }
+            }
+            catch (Exception ex)
+            {
+                LogError($"[Localization] Failed to load locale resource '{resourceName}': {ex.Message}");
+            }
+        }
+    }
+
+    /// <summary>
+    /// Sets the active language and notifies subscribers if changed.
+    /// </summary>
+    public static void SetLanguage(SystemLanguage language, bool notify = true)
+    {
+        var localeCode = LanguageToLocaleCode(language);
+        if (!Locales.ContainsKey(localeCode))
+        {
+            // Fallback to English if translation for this language does not exist
+            localeCode = FallbackLocaleCode;
+        }
+
+        var isChanged = (language != CurrentLanguage) || (localeCode != CurrentLocaleCode);
+
+        CurrentLanguage = language;
+        CurrentLocaleCode = localeCode;
+
+        if (isChanged && notify)
+        {
+            LogMsg($"[Localization] Language changed to: {CurrentLanguage} ({CurrentLocaleCode})");
+            try
+            {
+                OnLanguageChanged?.Invoke(CurrentLanguage);
+            }
+            catch (Exception ex)
+            {
+                LogError($"[Localization] Error during OnLanguageChanged notification: {ex.Message}");
+            }
+        }
+    }
+
+    /// <summary>
+    /// Retrieves a localized string for the specified key.
+    /// </summary>
+    public static string Get(string key)
+    {
+        if (string.IsNullOrEmpty(key)) return string.Empty;
+
+        // 1. Try currently active locale
+        if (Locales.TryGetValue(CurrentLocaleCode, out var activeDict) && activeDict.TryGetValue(key, out var val))
+        {
+            return val;
+        }
+
+        // 2. Fallback to English locale
+        if (CurrentLocaleCode != FallbackLocaleCode &&
+            Locales.TryGetValue(FallbackLocaleCode, out var fallbackDict) &&
+            fallbackDict.TryGetValue(key, out var fallbackVal))
+        {
+            return fallbackVal;
+        }
+
+        // 3. Fallback to raw key if missing
+        return key;
+    }
+
+    /// <summary>
+    /// Retrieves a formatted localized string.
+    /// </summary>
+    public static string Get(string key, params object[] args)
+    {
+        var template = Get(key);
+        if (args == null || args.Length == 0) return template;
+
+        try
+        {
+            return string.Format(template, args);
+        }
+        catch (FormatException)
+        {
+            return template;
+        }
+    }
+
+    /// <summary>
+    /// Maps Unity's SystemLanguage enum to an internal locale code.
+    /// </summary>
+    private static string LanguageToLocaleCode(SystemLanguage language)
+    {
+        return language switch
+        {
+            SystemLanguage.Korean => "ko",
+            SystemLanguage.English => "en",
+            _ => "en"
+        };
+    }
+
+    /// <summary>
+    /// Attempts to read the game's current language from RDString or Persistence.
+    /// </summary>
+    private static SystemLanguage DetectGameLanguage()
+    {
+        try
+        {
+            // First attempt: RDString.language
+            return RDString.language;
+        }
+        catch
+        {
+            try
+            {
+                // Fallback attempt: Persistence.language
+                return Persistence.language;
+            }
+            catch
+            {
+                return SystemLanguage.English;
+            }
+        }
+    }
+}
+
+/// <summary>
+/// Convenient shorthand alias for <see cref="LocalizationManager"/>.
+/// </summary>
+internal static class I18n
+{
+    /// <inheritdoc cref="LocalizationManager.Get(string)"/>
+    public static string Get(string key) => LocalizationManager.Get(key);
+
+    /// <inheritdoc cref="LocalizationManager.Get(string, object[])"/>
+    public static string Get(string key, params object[] args) => LocalizationManager.Get(key, args);
+
+    /// <inheritdoc cref="LocalizationManager.CurrentLanguage"/>
+    public static SystemLanguage CurrentLanguage => LocalizationManager.CurrentLanguage;
+
+    /// <inheritdoc cref="LocalizationManager.CurrentLocaleCode"/>
+    public static string CurrentLocaleCode => LocalizationManager.CurrentLocaleCode;
+
+    /// <inheritdoc cref="LocalizationManager.OnLanguageChanged"/>
+    public static event Action<SystemLanguage>? OnLanguageChanged
+    {
+        add => LocalizationManager.OnLanguageChanged += value;
+        remove => LocalizationManager.OnLanguageChanged -= value;
+    }
+}
diff --git a/Patch/Game/LanguageSyncPatch.cs b/Patch/Game/LanguageSyncPatch.cs
new file mode 100644
index 0000000..88daa71
--- /dev/null
+++ b/Patch/Game/LanguageSyncPatch.cs
@@ -0,0 +1,26 @@
+using ADOFAIRenderer.Localization;
+using HarmonyLib;
+using UnityEngine;
+
+namespace ADOFAIRenderer.Patch.Game;
+
+/// <summary>
+/// Synchronizes mod localization with ADOFAI's in-game language settings.
+/// </summary>
+[HarmonyPatch(typeof(RDString))]
+internal static class LanguageSyncPatch
+{
+    [HarmonyPatch(nameof(RDString.ChangeLanguage))]
+    [HarmonyPostfix]
+    public static void OnChangeLanguage(SystemLanguage language)
+    {
+        LocalizationManager.SetLanguage(language);
+    }
+
+    [HarmonyPatch(nameof(RDString.Setup))]
+    [HarmonyPostfix]
+    public static void OnSetup()
+    {
+        LocalizationManager.SetLanguage(RDString.language);
+    }
+}