diff --git a/Legacy/Legacy.csproj b/Legacy/Legacy.csproj
index 8d6feedf..892fc10b 100644
--- a/Legacy/Legacy.csproj
+++ b/Legacy/Legacy.csproj
@@ -83,6 +83,7 @@
     <Compile Include="Iris\ArcFPACK.cs" />
     <Compile Include="Jupiter\ArcLB5.cs" />
     <Compile Include="Lune\ArcPACK.cs" />
+    <Compile Include="Marron\ArcCPN.cs" />
     <Compile Include="Mina\ArcML2.cs" />
     <Compile Include="Mina\ImageMD.cs" />
     <Compile Include="Mink\ArcMINK.cs" />
diff --git a/Legacy/Marron/ArcCPN.cs b/Legacy/Marron/ArcCPN.cs
new file mode 100644
index 00000000..aa761fbd
--- /dev/null
+++ b/Legacy/Marron/ArcCPN.cs
@@ -0,0 +1,108 @@
+//! \file       ArcCPN.cs
+//! \date       2018 Feb 14
+//! \brief      Marron resource archive.
+//
+// Copyright (C) 2018 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 System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.IO;
+using System.Text.RegularExpressions;
+
+// [010727][Marron] Cosmos no Sora ni
+
+namespace GameRes.Formats.Marron
+{
+    internal class CpnArchive : ArcFile
+    {
+        public readonly byte Key;
+
+        public CpnArchive (ArcView arc, ArchiveFormat impl, ICollection<Entry> dir, byte key)
+            : base (arc, impl, dir)
+        {
+            Key = key;
+        }
+    }
+
+    [Export(typeof(ArchiveFormat))]
+    public class DatOpener : ArchiveFormat
+    {
+        public override string         Tag { get { return "DAT/CPN"; } }
+        public override string Description { get { return "Marron resource archive"; } }
+        public override uint     Signature { get { return 0; } }
+        public override bool  IsHierarchic { get { return true; } }
+        public override bool      CanWrite { get { return false; } }
+
+        static readonly Regex CpnEntryRe = new Regex (@"#(?:\./)?(?<name>[^$]+)\$(?<offset>\d+)\*(?<size>\d+)\+");
+
+        public override ArcFile TryOpen (ArcView file)
+        {
+            if (!file.Name.HasExtension (".dat"))
+                return null;
+            var cpn_name = Path.ChangeExtension (file.Name, ".cpn");
+            if (!VFS.FileExists (cpn_name))
+                return null;
+            byte key;
+            string cpn_index;
+            using (var cpn = VFS.OpenView (cpn_name))
+            {
+                key = cpn.View.ReadByte (0);
+                var cpn_data = cpn.View.ReadBytes (1, (uint)(cpn.MaxOffset - 1));
+                for (int i = 0; i < cpn_data.Length; ++i)
+                    cpn_data[i] ^= key;
+                cpn_index = Encodings.cp932.GetString (cpn_data);
+            }
+            int idx = cpn_index.IndexOf ('#', 1);
+            if (idx <= 1)
+                return null;
+            var data_name = cpn_index.Substring (1, idx-1);
+            if (!VFS.IsPathEqualsToFileName (file.Name, data_name))
+                return null;
+            var dir = new List<Entry>();
+            var match = CpnEntryRe.Match (cpn_index, idx);
+            while (match.Success)
+            {
+                var name = match.Groups["name"].Value;
+                var entry = FormatCatalog.Instance.Create<Entry> (name);
+                entry.Offset = UInt32.Parse (match.Groups["offset"].Value);
+                entry.Size   = UInt32.Parse (match.Groups["size"].Value);
+                if (!entry.CheckPlacement (file.MaxOffset))
+                    return null;
+                dir.Add (entry);
+                match = match.NextMatch();
+            }
+            if (0 == dir.Count)
+                return null;
+            return new CpnArchive (file, this, dir, key);
+        }
+
+        public override Stream OpenEntry (ArcFile arc, Entry entry)
+        {
+            var input = arc.File.CreateStream (entry.Offset, entry.Size);
+            var carc = arc as CpnArchive;
+            if (null == carc)
+                return input;
+            return new XoredStream (input, carc.Key);
+        }
+    }
+}