Restructured the project structure back to the way it was, there's no reasonable way to split the modules

src/NadekoBot/Modules/Games/Nunchi/NunchiCommands.cs

@@ -0,0 +1,111 @@
+#nullable disable
+using NadekoBot.Modules.Games.Common.Nunchi;
+using NadekoBot.Modules.Games.Services;
+
+namespace NadekoBot.Modules.Games;
+
+public partial class Games
+{
+    [Group]
+    public partial class NunchiCommands : NadekoModule<GamesService>
+    {
+        private readonly DiscordSocketClient _client;
+
+        public NunchiCommands(DiscordSocketClient client)
+            => _client = client;
+
+        [Cmd]
+        [RequireContext(ContextType.Guild)]
+        public async Task Nunchi()
+        {
+            var newNunchi = new NunchiGame(ctx.User.Id, ctx.User.ToString());
+            NunchiGame nunchi;
+
+            //if a game was already active
+            if ((nunchi = _service.NunchiGames.GetOrAdd(ctx.Guild.Id, newNunchi)) != newNunchi)
+            {
+                // join it
+                if (!await nunchi.Join(ctx.User.Id, ctx.User.ToString()))
+                    // if you failed joining, that means game is running or just ended
+                    // await ReplyErrorLocalized("nunchi_already_started");
+                    return;
+
+                await ReplyErrorLocalizedAsync(strs.nunchi_joined(nunchi.ParticipantCount));
+                return;
+            }
+
+
+            try { await ConfirmLocalizedAsync(strs.nunchi_created); }
+            catch { }
+
+            nunchi.OnGameEnded += NunchiOnGameEnded;
+            //nunchi.OnGameStarted += Nunchi_OnGameStarted;
+            nunchi.OnRoundEnded += Nunchi_OnRoundEnded;
+            nunchi.OnUserGuessed += Nunchi_OnUserGuessed;
+            nunchi.OnRoundStarted += Nunchi_OnRoundStarted;
+            _client.MessageReceived += ClientMessageReceived;
+
+            var success = await nunchi.Initialize();
+            if (!success)
+            {
+                if (_service.NunchiGames.TryRemove(ctx.Guild.Id, out var game))
+                    game.Dispose();
+                await ConfirmLocalizedAsync(strs.nunchi_failed_to_start);
+            }
+
+            Task ClientMessageReceived(SocketMessage arg)
+            {
+                _ = Task.Run(async () =>
+                {
+                    if (arg.Channel.Id != ctx.Channel.Id)
+                        return;
+
+                    if (!int.TryParse(arg.Content, out var number))
+                        return;
+                    try
+                    {
+                        await nunchi.Input(arg.Author.Id, arg.Author.ToString(), number);
+                    }
+                    catch
+                    {
+                    }
+                });
+                return Task.CompletedTask;
+            }
+
+            Task NunchiOnGameEnded(NunchiGame arg1, string arg2)
+            {
+                if (_service.NunchiGames.TryRemove(ctx.Guild.Id, out var game))
+                {
+                    _client.MessageReceived -= ClientMessageReceived;
+                    game.Dispose();
+                }
+
+                if (arg2 is null)
+                    return ConfirmLocalizedAsync(strs.nunchi_ended_no_winner);
+                return ConfirmLocalizedAsync(strs.nunchi_ended(Format.Bold(arg2)));
+            }
+        }
+
+        private Task Nunchi_OnRoundStarted(NunchiGame arg, int cur)
+            => ConfirmLocalizedAsync(strs.nunchi_round_started(Format.Bold(arg.ParticipantCount.ToString()),
+                Format.Bold(cur.ToString())));
+
+        private Task Nunchi_OnUserGuessed(NunchiGame arg)
+            => ConfirmLocalizedAsync(strs.nunchi_next_number(Format.Bold(arg.CurrentNumber.ToString())));
+
+        private Task Nunchi_OnRoundEnded(NunchiGame arg1, (ulong Id, string Name)? arg2)
+        {
+            if (arg2.HasValue)
+                return ConfirmLocalizedAsync(strs.nunchi_round_ended(Format.Bold(arg2.Value.Name)));
+            return ConfirmLocalizedAsync(strs.nunchi_round_ended_boot(
+                Format.Bold("\n"
+                            + string.Join("\n, ",
+                                arg1.Participants.Select(x
+                                    => x.Name))))); // this won't work if there are too many users
+        }
+
+        private Task Nunchi_OnGameStarted(NunchiGame arg)
+            => ConfirmLocalizedAsync(strs.nunchi_started(Format.Bold(arg.ParticipantCount.ToString())));
+    }
+}