diff --git a/ArcFormats/Mugi/ArcBIN.cs b/ArcFormats/Mugi/ArcBIN.cs
new file mode 100644
index 00000000..0b789208
--- /dev/null
+++ b/ArcFormats/Mugi/ArcBIN.cs
@@ -0,0 +1,94 @@
+//! \file       ArcBIN.cs
+//! \date       2023 Sep 03
+//! \brief      Mugi's resource archive.
+//
+// Copyright (C) 2023 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using GameRes.Compression;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.IO;
+
+// [070323][schoolzone] Cosplay! Kyonyuu Mahjong
+
+namespace GameRes.Formats.Mugi
+{
+    [Export(typeof(ArchiveFormat))]
+    public class BinOpener : ArchiveFormat
+    {
+        public override string         Tag { get => "BIN/MUGI"; }
+        public override string Description { get => "Mugi's resource archive"; }
+        public override uint     Signature { get => 0; }
+        public override bool  IsHierarchic { get => false; }
+        public override bool      CanWrite { get => false; }
+
+        public override ArcFile TryOpen (ArcView file)
+        {
+            const uint index_size = 0x8000 + 0x4000;
+            if (file.MaxOffset <= index_size)
+                return null;
+            file.View.Reserve (0, index_size);
+            uint index_pos = 0x8000;
+            uint offset = file.View.ReadUInt32 (index_pos);
+            if (offset != index_size)
+                return null;
+            uint[] offsets = new uint[0x800];
+            int count = 0;
+            while (offset != file.MaxOffset)
+            {
+                if (count == offsets.Length)
+                    return null;
+                offsets[count++] = offset;
+                index_pos += 4;
+                offset = file.View.ReadUInt32 (index_pos);
+                if (offset < offsets[count-1] || offset > file.MaxOffset)
+                    return null;
+            }
+            offsets[count--] = offset;
+            uint name_pos = 0;
+            uint size_pos = 0xA000;
+            var dir = new List<Entry> (count);
+            for (int i = 0; i < count; ++i)
+            {
+                var name = file.View.ReadString (name_pos, 0x10);
+                var entry = Create<PackedEntry> (name);
+                entry.Offset = offsets[i];
+                entry.Size = (uint)(offsets[i+1] - offsets[i]);
+                entry.UnpackedSize = file.View.ReadUInt32 (size_pos);
+                entry.IsPacked = entry.Size != entry.UnpackedSize;
+                dir.Add (entry);
+                name_pos += 0x10;
+                size_pos += 4;
+            }
+            return new ArcFile (file, this, dir);
+        }
+
+        public override Stream OpenEntry (ArcFile arc, Entry entry)
+        {
+            var pent = (PackedEntry)entry;
+            Stream input = arc.File.CreateStream (entry.Offset, entry.Size);
+            if (pent.IsPacked)
+                input = new LzssStream (input);
+            return input;
+        }
+    }
+}