diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index 27cd5d01..2d0c86df 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -57,6 +57,7 @@
     <Compile Include="ArcAMI.cs" />
     <Compile Include="ArcINT.cs" />
     <Compile Include="ArcNPA.cs" />
+    <Compile Include="ArcSteinsGate.cs" />
     <Compile Include="ArcXFL.cs" />
     <Compile Include="ArcXP3.cs" />
     <Compile Include="ArcYPF.cs" />
diff --git a/ArcFormats/ArcSteinsGate.cs b/ArcFormats/ArcSteinsGate.cs
new file mode 100644
index 00000000..4c6c0544
--- /dev/null
+++ b/ArcFormats/ArcSteinsGate.cs
@@ -0,0 +1,111 @@
+//! \file       ArcSteinsGate.cs
+//! \date       Thu Jul 24 23:36:01 2014
+//! \brief      Nitro+ Steins;Gate archive implementation.
+//
+
+using System.IO;
+using System.Text;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using GameRes.Formats.Strings;
+using GameRes.Utility;
+
+namespace GameRes.Formats
+{
+    [Export(typeof(ArchiveFormat))]
+    public class NpaSteinsGateOpener : ArchiveFormat
+    {
+        public override string Tag { get { return "NPA"; } }
+        public override string Description { get { return arcStrings.NPASteinsGateDescription; } }
+        public override uint Signature { get { return 0; } }
+        public override bool IsHierarchic { get { return true; } }
+
+        internal static readonly byte[] KeyString = {
+            'B'^0xff, 'U'^0xff, 'C'^0xff, 'K'^0xff,
+            'T'^0xff, 'I'^0xff, 'C'^0xff, 'K'^0xff
+        };
+
+        public override ArcFile TryOpen (ArcView file)
+        {
+            int index_size = file.View.ReadInt32 (0);
+            if (index_size < 0x14 || index_size >= file.MaxOffset || index_size > 0xffffff)
+                return null;
+
+            var stream = new SteinsGateEncryptedStream (file, 4, (uint)index_size);
+            using (var header = new BinaryReader (stream, Encoding.Unicode))
+            {
+                int entry_count = header.ReadInt32();
+                if (entry_count <= 0)
+                    return null;
+                int average_entry_size = index_size / entry_count;
+                if (average_entry_size < 0x11)
+                    return null;
+
+                var dir = new List<Entry> ((int)entry_count);
+                for (uint i = 0; i < entry_count; ++i)
+                {
+                    int name_length = header.ReadInt32();
+                    if (name_length+0x10 > index_size)
+                        return null;
+                    string filename = new string (header.ReadChars (name_length/2));
+
+                    var entry = FormatCatalog.Instance.CreateEntry (filename);
+                    entry.Size = header.ReadUInt32();
+                    entry.Offset = header.ReadInt64();
+                    if (!entry.CheckPlacement (file.MaxOffset))
+                        return null;
+                    dir.Add (entry);
+
+                    index_size -= name_length+0x10;
+                }
+                return new ArcFile (file, this, dir);
+            }
+        }
+
+        public override Stream OpenEntry (ArcFile arc, Entry entry)
+        {
+            return new SteinsGateEncryptedStream (arc.File, entry.Offset, entry.Size);
+        }
+
+        internal void Encrypt (byte[] buffer, int offset, int count)
+        {
+            for (int i = 0; i < count; ++i)
+            {
+                buffer[offset+i] ^= KeyString[i & 7];
+            }
+        }
+    }
+
+    public class SteinsGateEncryptedStream : ArcView.ArcStream
+    {
+        public SteinsGateEncryptedStream (ArcView file, long offset, uint size)
+            : base (file, offset, size)
+        {
+        }
+
+        public override int Read (byte[] buffer, int offset, int count)
+        {
+            int position = (int)Position & 7;
+            int read = base.Read (buffer, offset, count);
+            if (read > 0)
+            {
+                for (int i = 0; i < read; ++i)
+                {
+                    buffer[offset+i] ^= NpaSteinsGateOpener.KeyString[(position+i)&7];
+                }
+            }
+            return read;
+        }
+
+        public override int ReadByte ()
+        {
+            int position = (int)Position & 7;
+            int b = base.ReadByte();
+            if (-1 != b)
+            {
+                b ^= NpaSteinsGateOpener.KeyString[position];
+            }
+            return b;
+        }
+    }
+}
diff --git a/ArcFormats/Strings/arcStrings.Designer.cs b/ArcFormats/Strings/arcStrings.Designer.cs
index 35c795c3..e961c210 100644
--- a/ArcFormats/Strings/arcStrings.Designer.cs
+++ b/ArcFormats/Strings/arcStrings.Designer.cs
@@ -180,6 +180,15 @@ namespace GameRes.Formats.Strings {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Nitro+ Steins;Gate resource archive.
+        /// </summary>
+        public static string NPASteinsGateDescription {
+            get {
+                return ResourceManager.GetString("NPASteinsGateDescription", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Amaterasu Translations Muv-Luv script file.
         /// </summary>