diff --git a/lib/foundation/comic_source/models.dart b/lib/foundation/comic_source/models.dart
index 9d439bb..4be9310 100644
--- a/lib/foundation/comic_source/models.dart
+++ b/lib/foundation/comic_source/models.dart
@@ -376,7 +376,7 @@ class ComicChapters {
     return _groupedChapters![group] ?? {};
   }
 
-  /// Get a group of chapters by index
+  /// Get a group of chapters by index(0-based)
   Map<String, String> getGroupByIndex(int index) {
     return _groupedChapters!.values.elementAt(index);
   }
diff --git a/lib/foundation/history.dart b/lib/foundation/history.dart
index 87edb15..0c017cf 100644
--- a/lib/foundation/history.dart
+++ b/lib/foundation/history.dart
@@ -50,17 +50,24 @@ class History implements Comic {
   @override
   String cover;
 
+  /// index of chapters. 1-based.
   int ep;
 
+  /// index of pages. 1-based.
   int page;
 
+  /// index of chapter groups. 1-based.
+  /// If [group] is not null, [ep] is the index of chapter in the group.
+  int? group;
+
   @override
   String id;
 
   /// readEpisode is a set of episode numbers that have been read.
-  ///
-  /// The number of episodes is 1-based.
-  Set<int> readEpisode;
+  /// For normal chapters, it is a set of chapter numbers.
+  /// For grouped chapters, it is a set of strings in the format of "group_number-chapter_number".
+  /// 1-based.
+  Set<String> readEpisode;
 
   @override
   int? maxPage;
@@ -69,29 +76,17 @@ class History implements Comic {
       {required HistoryMixin model,
       required this.ep,
       required this.page,
-      Set<int>? readChapters,
+      this.group,
+      Set<String>? readChapters,
       DateTime? time})
       : type = model.historyType,
         title = model.title,
         subtitle = model.subTitle ?? '',
         cover = model.cover,
         id = model.id,
-        readEpisode = readChapters ?? <int>{},
+        readEpisode = readChapters ?? <String>{},
         time = time ?? DateTime.now();
 
-  Map<String, dynamic> toMap() => {
-        "type": type.value,
-        "time": time.millisecondsSinceEpoch,
-        "title": title,
-        "subtitle": subtitle,
-        "cover": cover,
-        "ep": ep,
-        "page": page,
-        "id": id,
-        "readEpisode": readEpisode.toList(),
-        "max_page": maxPage
-      };
-
   History.fromMap(Map<String, dynamic> map)
       : type = HistoryType(map["type"]),
         time = DateTime.fromMillisecondsSinceEpoch(map["time"]),
@@ -101,8 +96,9 @@ class History implements Comic {
         ep = map["ep"],
         page = map["page"],
         id = map["id"],
-        readEpisode = Set<int>.from(
-            (map["readEpisode"] as List<dynamic>?)?.toSet() ?? const <int>{}),
+        readEpisode = Set<String>.from(
+            (map["readEpisode"] as List<dynamic>?)?.toSet() ??
+                const <String>{}),
         maxPage = map["max_page"];
 
   @override
@@ -119,11 +115,11 @@ class History implements Comic {
         ep = row["ep"],
         page = row["page"],
         id = row["id"],
-        readEpisode = Set<int>.from((row["readEpisode"] as String)
+        readEpisode = Set<String>.from((row["readEpisode"] as String)
             .split(',')
-            .where((element) => element != "")
-            .map((e) => int.parse(e))),
-        maxPage = row["max_page"];
+            .where((element) => element != "")),
+        maxPage = row["max_page"],
+        group = row["chapter_group"];
 
   @override
   bool operator ==(Object other) {
@@ -212,18 +208,24 @@ class HistoryManager with ChangeNotifier {
           ep int,
           page int,
           readEpisode text,
-          max_page int
+          max_page int,
+          chapter_group int
         );
       """);
 
+    var columns = _db.select("PRAGMA table_info(history);");
+    if (!columns.any((element) => element["name"] == "chapter_group")) {
+      _db.execute("alter table history add column chapter_group int;");
+    }
+
     notifyListeners();
     ImageFavoriteManager().init();
     isInitialized = true;
   }
 
-  static const  _insertHistorySql = """
-        insert or replace into history (id, title, subtitle, cover, time, type, ep, page, readEpisode, max_page)
-        values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
+  static const _insertHistorySql = """
+        insert or replace into history (id, title, subtitle, cover, time, type, ep, page, readEpisode, max_page, chapter_group)
+        values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
       """;
 
   static Future<void> _addHistoryAsync(int dbAddr, History newItem) {
@@ -239,7 +241,8 @@ class HistoryManager with ChangeNotifier {
         newItem.ep,
         newItem.page,
         newItem.readEpisode.join(','),
-        newItem.maxPage
+        newItem.maxPage,
+        newItem.group
       ]);
     });
   }
@@ -281,7 +284,8 @@ class HistoryManager with ChangeNotifier {
       newItem.ep,
       newItem.page,
       newItem.readEpisode.join(','),
-      newItem.maxPage
+      newItem.maxPage,
+      newItem.group
     ]);
     if (_cachedHistoryIds == null) {
       updateCache();
diff --git a/lib/foundation/local.dart b/lib/foundation/local.dart
index 2d19c34..c2b462c 100644
--- a/lib/foundation/local.dart
+++ b/lib/foundation/local.dart
@@ -115,6 +115,7 @@ class LocalComic with HistoryMixin implements Comic {
         chapters: chapters,
         initialChapter: history?.ep,
         initialPage: history?.page,
+        initialChapterGroup: history?.group,
         history: history ??
             History.fromModel(
               model: this,
diff --git a/lib/pages/comic_details_page/chapters.dart b/lib/pages/comic_details_page/chapters.dart
index 2f13089..0a9586f 100644
--- a/lib/pages/comic_details_page/chapters.dart
+++ b/lib/pages/comic_details_page/chapters.dart
@@ -286,8 +286,13 @@ class _GroupedComicChaptersState extends State<_GroupedComicChapters>
                     }
                     chapterIndex += chapters.getGroupByIndex(j).length;
                   }
-                  bool visited =
-                      (history?.readEpisode ?? {}).contains(chapterIndex + 1);
+                  String rawIndex = (chapterIndex + 1).toString();
+                  String groupedIndex = "${index + 1}-${i + 1}";
+                  bool visited = false;
+                  if (history != null) {
+                    visited = history!.readEpisode.contains(groupedIndex) ||
+                        history!.readEpisode.contains(rawIndex);
+                  }
                   return Padding(
                     padding: const EdgeInsets.fromLTRB(6, 4, 6, 4),
                     child: Material(
diff --git a/lib/pages/comic_details_page/comic_page.dart b/lib/pages/comic_details_page/comic_page.dart
index de3a662..fef8424 100644
--- a/lib/pages/comic_details_page/comic_page.dart
+++ b/lib/pages/comic_details_page/comic_page.dart
@@ -167,6 +167,7 @@ class _ComicPageState extends LoadingState<ComicPage, ComicDetails>
               chapters: localComic.chapters,
               initialPage: history?.page,
               initialChapter: history?.ep,
+              initialChapterGroup: history?.group,
               history: history ??
                   History.fromModel(
                     model: localComic,
@@ -383,11 +384,19 @@ class _ComicPageState extends LoadingState<ComicPage, ComicDetails>
                       bool haveChapter = comic.chapters != null;
                       var page = history!.page;
                       var ep = history!.ep;
+                      var group = history!.group;
                       String text;
                       if (haveChapter) {
+                        var epName = group == null
+                            ? comic.chapters!.titles.elementAt(
+                                math.min(ep - 1, comic.chapters!.length - 1),
+                              )
+                            : comic.chapters!
+                                .getGroupByIndex(group - 1)
+                                .values
+                                .elementAt(ep - 1);
                         text = "Last Reading: @epName Page @page".tlParams({
-                          'epName': comic.chapters!.titles.elementAt(
-                              math.min(ep - 1, comic.chapters!.length - 1)),
+                          'epName': epName,
                           'page': page,
                         });
                       } else {
diff --git a/lib/pages/reader/loading.dart b/lib/pages/reader/loading.dart
index e8a09d4..d8fb732 100644
--- a/lib/pages/reader/loading.dart
+++ b/lib/pages/reader/loading.dart
@@ -33,6 +33,7 @@ class _ReaderWithLoadingState
       history: data.history,
       initialChapter: widget.initialEp ?? data.history.ep,
       initialPage: widget.initialPage ?? data.history.page,
+      initialChapterGroup: data.history.group,
       author: data.author,
       tags: data.tags,
     );
diff --git a/lib/pages/reader/reader.dart b/lib/pages/reader/reader.dart
index 4e3d139..8e1412f 100644
--- a/lib/pages/reader/reader.dart
+++ b/lib/pages/reader/reader.dart
@@ -62,6 +62,7 @@ class Reader extends StatefulWidget {
     required this.history,
     this.initialPage,
     this.initialChapter,
+    this.initialChapterGroup,
     required this.author,
     required this.tags,
   });
@@ -84,6 +85,9 @@ class Reader extends StatefulWidget {
   /// Starts from 1, invalid values equal to 1
   final int? initialChapter;
 
+  /// Starts from 1, invalid values equal to 1
+  final int? initialChapterGroup;
+
   final History history;
 
   @override
@@ -147,13 +151,18 @@ class _ReaderState extends State<Reader> with _ReaderLocation, _ReaderWindow {
   @override
   void initState() {
     page = widget.initialPage ?? 1;
-    chapter = widget.initialChapter ?? 1;
     if (page < 1) {
       page = 1;
     }
+    chapter = widget.initialChapter ?? 1;
     if (chapter < 1) {
       chapter = 1;
     }
+    if (widget.initialChapterGroup != null) {
+      for (int i=0; i<(widget.initialChapterGroup!-1); i++) {
+        chapter += widget.chapters!.getGroupByIndex(i).length;
+      }
+    }
     if (widget.initialPage != null) {
       page = (widget.initialPage! / imagesPerPage).ceil();
     }
@@ -238,11 +247,23 @@ class _ReaderState extends State<Reader> with _ReaderLocation, _ReaderWindow {
   void updateHistory() {
     if (history != null) {
       history!.page = page;
-      history!.ep = chapter;
       if (maxPage > 1) {
         history!.maxPage = maxPage;
       }
-      history!.readEpisode.add(chapter);
+      if (widget.chapters?.isGrouped ?? false) {
+        int g = 0;
+        int c = chapter;
+        while (c > widget.chapters!.getGroupByIndex(g).length) {
+          c -= widget.chapters!.getGroupByIndex(g).length;
+          g++;
+        }
+        history!.readEpisode.add('${g + 1}-$c');
+        history!.ep = c;
+        history!.group = g+1;
+      } else {
+        history!.readEpisode.add(chapter.toString());
+        history!.ep = chapter;
+      }
       history!.time = DateTime.now();
       _updateHistoryTimer?.cancel();
       _updateHistoryTimer = Timer(const Duration(seconds: 1), () {