diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index 6e5bd09e..e4a716ef 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -192,6 +192,7 @@
     <Compile Include="MAGES\ArcLoveOnce.cs" />
     <Compile Include="MAGES\ImageBIN.cs" />
     <Compile Include="Mugi\ArcBIN.cs" />
+    <Compile Include="Musica\ArcPAK.cs" />
     <Compile Include="NipponIchi\ArcCASN.cs" />
     <Compile Include="NipponIchi\ArcPSFS.cs" />
     <Compile Include="NipponIchi\ImageNMT.cs" />
diff --git a/ArcFormats/Musica/ArcPAK.cs b/ArcFormats/Musica/ArcPAK.cs
new file mode 100644
index 00000000..d090af84
--- /dev/null
+++ b/ArcFormats/Musica/ArcPAK.cs
@@ -0,0 +1,173 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.IO;
+using System.Text;
+
+namespace GameRes.Formats.Musica
+{
+    [Export(typeof(ArchiveFormat))]
+    public class PakOpener : ArchiveFormat
+    {
+        public override string Tag { get; } = "PAK";
+        public override string Description { get; } = "Musica engine legacy resource archive";
+        public override uint Signature { get; } = 0;
+        public override bool IsHierarchic { get; } = true;
+        public override bool CanWrite { get; } = false;
+
+        public PakOpener()
+        {
+            Extensions = new[] { "pak" };
+            ContainedFormats = new string[] { "PNG", "OGG" };
+        }
+
+        static readonly HashSet<string> PakImageNames = new HashSet<string>()
+        {
+            "bg", "st",
+        };
+
+        static readonly HashSet<string> PakAudioNames = new HashSet<string>()
+        {
+            "bgm", "se", "voice",
+        };
+
+        private string GetType(string pakName, string entryName)
+        {
+            if (PakImageNames.Contains(pakName))
+            {
+                return "image";
+            }
+
+            if (PakAudioNames.Contains(pakName))
+            {
+                return "audio";
+            }
+
+            return FormatCatalog.Instance.GetTypeFromName(entryName, ContainedFormats);
+        }
+
+        public override ArcFile TryOpen(ArcView view)
+        {
+            Stream input = view.CreateStream();
+            using(input = new NegStream(input))
+            {
+                using(ArcView.Reader reader = new ArcView.Reader(input))
+                {
+                    int count = reader.ReadInt32();
+                    if (count <= 0)
+                    {
+                        return null;
+                    }
+
+                    List<Entry> entries = new List<Entry>(count);
+                    for(int i = 0; i < count; ++i)
+                    {
+                        uint indexLen = reader.ReadUInt32();
+                        long indexStart = input.Position;
+
+                        string name = input.ReadCString();
+                        if (string.IsNullOrWhiteSpace(name))
+                        {
+                            return null;
+                        }
+                        uint size = reader.ReadUInt32();
+                        uint offset = reader.ReadUInt32();
+
+                        Entry entry = new Entry() { Name = name, Offset = offset, Size = size };
+                        if (!entry.CheckPlacement(view.MaxOffset))
+                        {
+                            return null;
+                        }
+                        entry.Type = this.GetType(Path.GetFileNameWithoutExtension(view.Name), entry.Name);
+                        entries.Add(entry);
+
+                        input.Position = indexStart + indexLen;
+                    }
+                    return new PakArchive(view, this, entries, input.Position);
+                }
+            }
+        }
+
+        public override Stream OpenEntry(ArcFile arc, Entry entry)
+        {
+            if (!(arc is PakArchive pakArc))
+            {
+                return base.OpenEntry(arc, entry);
+            }
+
+            return new NegStream(base.OpenEntry(arc, pakArc.GetEntry(entry)));
+        }
+    }
+
+    internal class PakArchive : ArcFile
+    {
+        private long m_IndexSize;
+        public PakArchive(ArcView arc, ArchiveFormat impl, ICollection<Entry> dir, long indexSize) : base(arc, impl, dir)
+        {
+            m_IndexSize = indexSize;
+        }
+
+        public Entry GetEntry(Entry e)
+        {
+            return new Entry
+            {
+                Name = e.Name,
+                Offset = e.Offset + m_IndexSize,
+                Size = e.Size,
+                Type = e.Type,
+            };
+        }
+    }
+
+    //neg reg8
+    public class NegStream : ProxyStream
+    {
+        public NegStream(Stream stream, bool leave_open = false) : base(stream, leave_open)
+        {
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            int read = BaseStream.Read(buffer, offset, count);
+            for (int i = 0; i < read; ++i)
+            {
+                buffer[offset + i] = (byte)-buffer[offset + i];
+            }
+            return read;
+        }
+
+        public override int ReadByte()
+        {
+            int b = BaseStream.ReadByte();
+            if (-1 != b)
+            {
+                b = (byte)-b;
+            }
+            return b;
+        }
+
+        byte[] write_buf;
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            if (null == write_buf)
+                write_buf = new byte[81920];
+            while (count > 0)
+            {
+                int chunk = Math.Min(write_buf.Length, count);
+                for (int i = 0; i < chunk; ++i)
+                {
+                    write_buf[i] = (byte)-buffer[offset + i];
+                }
+                BaseStream.Write(write_buf, 0, chunk);
+                offset += chunk;
+                count -= chunk;
+            }
+        }
+
+        public override void WriteByte(byte value)
+        {
+            BaseStream.WriteByte((byte)-value);
+        }
+    }
+}