diff --git a/lib/view/dialog/user_select_dialog.dart b/lib/view/dialog/user_select_dialog.dart
index e0e0b0bb..cdfcb81a 100644
--- a/lib/view/dialog/user_select_dialog.dart
+++ b/lib/view/dialog/user_select_dialog.dart
@@ -10,6 +10,7 @@ import '../../model/account.dart';
 import '../../provider/api/i_notifier_provider.dart';
 import '../../provider/api/search_users_by_username_provider.dart';
 import '../../provider/recently_used_users_notifier_provider.dart';
+import '../../util/punycode.dart';
 import '../widget/error_message.dart';
 import '../widget/user_preview.dart';
 import '../widget/user_sheet.dart';
@@ -51,8 +52,8 @@ class UserSelectDialog extends HookConsumerWidget {
         ? ref.watch(
             searchUsersByUsernameProvider(
               account,
-              username.value,
-              host.value,
+              username.value.isNotEmpty ? username.value : null,
+              host.value.isNotEmpty ? toAscii(host.value) : null,
             ),
           )
         : null;
diff --git a/lib/view/widget/mfm_keyboard.dart b/lib/view/widget/mfm_keyboard.dart
index de6c7e6a..2d4085d2 100644
--- a/lib/view/widget/mfm_keyboard.dart
+++ b/lib/view/widget/mfm_keyboard.dart
@@ -20,6 +20,7 @@ import '../../provider/recently_used_users_notifier_provider.dart';
 import '../../provider/search_custom_emojis_provider.dart';
 import '../../provider/search_unicode_emojis_provider.dart';
 import '../../util/pick_date_time.dart';
+import '../../util/punycode.dart';
 import '../dialog/user_select_dialog.dart';
 import 'emoji_picker.dart';
 import 'emoji_widget.dart';
@@ -250,7 +251,8 @@ class MfmEmojiKeyboard extends HookConsumerWidget {
           final selectionIndex = max(0, controller.selection.start);
           final textBeforeSelection =
               controller.text.substring(0, selectionIndex);
-          final match = RegExp(r':?(\S*)$').firstMatch(textBeforeSelection);
+          final match = RegExp(r':(\S*)$').firstMatch(textBeforeSelection) ??
+              RegExp(r'(\S*)$').firstMatch(textBeforeSelection);
           query.value = match?[1] ?? '';
           final tagIndex = selectionIndex - (match?[0]?.length ?? 0) + 1;
           isAfterCloseTag.value =
@@ -413,9 +415,9 @@ class MfmFnKeyboard extends HookConsumerWidget {
           final selectionIndex = max(0, controller.selection.start);
           final textBeforeSelection =
               controller.text.substring(0, selectionIndex);
-          query.value =
-              RegExp(r'(\$\[)?(\S*)$').firstMatch(textBeforeSelection)?[2] ??
-                  '';
+          final match = RegExp(r'\$\[(\S*)$').firstMatch(textBeforeSelection) ??
+              RegExp(r'(\S*)$').firstMatch(textBeforeSelection);
+          query.value = match?[1] ?? '';
           periodIndex.value = query.value.indexOf('.');
         }
 
@@ -583,17 +585,23 @@ class MfmMentionKeyboard extends HookConsumerWidget {
           final selectionIndex = max(0, controller.selection.start);
           final textBeforeSelection =
               controller.text.substring(0, selectionIndex);
-          query.value =
-              RegExp(r'@?(\S*)$').firstMatch(textBeforeSelection)?[1] ?? '';
-          if (query.value case final query when query.isNotEmpty) {
-            final acct = query.split('@');
+          final match = RegExp(r'(@([a-zA-Z0-9_.-]+))?@([^@\s]*)$')
+              .firstMatch(textBeforeSelection);
+          query.value = match?[0]?.substring(1) ?? '';
+          final first = match?[2];
+          final second = match?[3];
+          final username = first ?? second;
+          final host = first != null && second != null ? toAscii(second) : null;
+          if (username != null) {
             users.value = await ref.read(
               searchUsersByUsernameProvider(
                 account,
-                acct.first,
-                acct.elementAtOrNull(1),
+                username,
+                host,
               ).future,
             );
+          } else {
+            users.value = [];
           }
         }
 
@@ -617,8 +625,9 @@ class MfmMentionKeyboard extends HookConsumerWidget {
                   account: account,
                   username: user.username,
                   host: user.host ?? account.host,
-                  onTap: () => controller.insert(
-                    '${user.acct.substring(query.value.length + 1)} ',
+                  onTap: () => controller.replace(
+                    query.value.length + 1,
+                    '${user.acct} ',
                   ),
                 ),
               ),
@@ -653,8 +662,9 @@ class MfmHashtagKeyboard extends HookConsumerWidget {
           final selectionIndex = max(0, controller.selection.start);
           final textBeforeSelection =
               controller.text.substring(0, selectionIndex);
-          query.value =
-              RegExp(r'#?(\S*)$').firstMatch(textBeforeSelection)?[1] ?? '';
+          final match = RegExp(r'#(\S*)$').firstMatch(textBeforeSelection) ??
+              RegExp(r'(\S*)$').firstMatch(textBeforeSelection);
+          query.value = match?[1] ?? '';
           if (query.value case final query when query.isNotEmpty) {
             hashtags.value =
                 await ref.read(searchHashtagsProvider(account, query).future);
diff --git a/test/view/widget/mfm_keyboard_test.dart b/test/view/widget/mfm_keyboard_test.dart
index 3988acc4..f722574f 100644
--- a/test/view/widget/mfm_keyboard_test.dart
+++ b/test/view/widget/mfm_keyboard_test.dart
@@ -37,11 +37,10 @@ Future<ProviderContainer> setupWidget(
 
 void main() {
   group('getLastTag', () {
-    final controller = TextEditingController();
-    final widget =
-        MfmKeyboard(account: Account.dummy(), controller: controller);
-
     test('emoji', () {
+      final controller = TextEditingController();
+      final widget =
+          MfmKeyboard(account: Account.dummy(), controller: controller);
       controller.text = ':';
       controller.selection = const TextSelection.collapsed(offset: 0);
       expect(widget.getLastTag(), equals((null, -1)));
@@ -58,6 +57,9 @@ void main() {
     });
 
     test('mfmFn', () {
+      final controller = TextEditingController();
+      final widget =
+          MfmKeyboard(account: Account.dummy(), controller: controller);
       controller.text = r'$[';
       controller.selection = const TextSelection.collapsed(offset: 0);
       expect(widget.getLastTag(), equals((null, -1)));
@@ -74,6 +76,9 @@ void main() {
     });
 
     test('mention', () {
+      final controller = TextEditingController();
+      final widget =
+          MfmKeyboard(account: Account.dummy(), controller: controller);
       controller.text = '@';
       controller.selection = const TextSelection.collapsed(offset: 0);
       expect(widget.getLastTag(), equals((null, -1)));
@@ -87,6 +92,9 @@ void main() {
     });
 
     test('hashtag', () {
+      final controller = TextEditingController();
+      final widget =
+          MfmKeyboard(account: Account.dummy(), controller: controller);
       controller.text = '#';
       controller.selection = const TextSelection.collapsed(offset: 0);
       expect(widget.getLastTag(), equals((null, -1)));
@@ -100,6 +108,9 @@ void main() {
     });
 
     test('mixed', () {
+      final controller = TextEditingController();
+      final widget =
+          MfmKeyboard(account: Account.dummy(), controller: controller);
       controller.text = r':emoji: #hashtag $[tada a] @user';
       controller.selection = const TextSelection.collapsed(offset: 0);
       expect(widget.getLastTag(), equals((null, -1)));
@@ -166,6 +177,26 @@ void main() {
         expect(controller.text, '❤️');
       });
 
+      testWidgets(
+        'should show an emoji keyboard if an open tag is between characters',
+        (tester) async {
+          const account = Account(host: 'misskey.tld', username: 'testuser');
+          final controller = TextEditingController(text: 'a:b');
+          controller.selection = const TextSelection.collapsed(offset: 2);
+          final container = await setupWidget(
+            tester,
+            account: account,
+            controller: controller,
+          );
+          await container
+              .read(accountSettingsNotifierProvider(account).notifier)
+              .setRecentlyUsedEmojis(['❤️']);
+          await tester.pumpAndSettle();
+          await tester.tap(find.byKey(const ValueKey('❤️')));
+          expect(controller.text, 'a❤️b');
+        },
+      );
+
       testWidgets('should not show an emoji keyboard after a close tag',
           (tester) async {
         const account = Account(host: 'misskey.tld', username: 'testuser');
@@ -252,6 +283,23 @@ void main() {
         expect(controller.text, r'$[spin.speed=1.5s,x');
       });
 
+      testWidgets(
+        'should show an MFM fn keyboard if an open tag is between characters',
+        (tester) async {
+          const account = Account(host: 'misskey.tld', username: 'testuser');
+          final controller = TextEditingController(text: r'a$[b');
+          controller.selection = const TextSelection.collapsed(offset: 3);
+          await setupWidget(
+            tester,
+            account: account,
+            controller: controller,
+          );
+          await tester.pumpAndSettle();
+          await tester.tap(find.text('tada'));
+          expect(controller.text, r'a$[tada b');
+        },
+      );
+
       testWidgets('should not show an MFM fn keyboard after a close tag',
           (tester) async {
         const account = Account(host: 'misskey.tld', username: 'testuser');
@@ -349,7 +397,27 @@ void main() {
         expect(controller.text, '@testuser@misskey2.tld ');
       });
 
-      testWidgets('should not show an mention keyboard after a space',
+      testWidgets(
+        'should show a mention keyboard if an open tag is between characters',
+        (tester) async {
+          const account = Account(host: 'misskey.tld', username: 'testuser');
+          final controller = TextEditingController(text: 'a:b');
+          controller.selection = const TextSelection.collapsed(offset: 2);
+          final container = await setupWidget(
+            tester,
+            account: account,
+            controller: controller,
+          );
+          await container
+              .read(accountSettingsNotifierProvider(account).notifier)
+              .setRecentlyUsedEmojis(['❤️']);
+          await tester.pumpAndSettle();
+          await tester.tap(find.byKey(const ValueKey('❤️')));
+          expect(controller.text, 'a❤️b');
+        },
+      );
+
+      testWidgets('should not show a mention keyboard after a space',
           (tester) async {
         const account = Account(host: 'misskey.tld', username: 'testuser');
         final controller = TextEditingController();