diff --git a/Assets/Cryville/Common/Math/FractionUtils.cs b/Assets/Cryville/Common/Math/FractionUtils.cs
new file mode 100644
index 0000000..a2d26ed
--- /dev/null
+++ b/Assets/Cryville/Common/Math/FractionUtils.cs
@@ -0,0 +1,52 @@
+using System;
+
+namespace Cryville.Common.Math {
+	/// <summary>
+	/// Provides a set of <see langword="static" /> methods related to fractions.
+	/// </summary>
+	public static class FractionUtils {
+		/// <summary>
+		/// Converts a <see cref="double" /> decimal to a fraction.
+		/// </summary>
+		/// <param name="value">The decimal.</param>
+		/// <param name="error">The error.</param>
+		/// <param name="n">The numerator.</param>
+		/// <param name="d">The denominator.</param>
+		/// <exception cref="ArgumentOutOfRangeException"><paramref name="value" /> is less than 0 or <paramref name="error" /> is not greater than 0 or not less than 1.</exception>
+		public static void ToFraction(double value, double error, out int n, out int d) {
+			if (value < 0.0)
+				throw new ArgumentOutOfRangeException("value", "Must be >= 0.");
+			if (error <= 0.0 || error >= 1.0)
+				throw new ArgumentOutOfRangeException("accuracy", "Must be > 0 and < 1.");
+
+			int num = (int)System.Math.Floor(value);
+			value -= num;
+
+			if (value < error) { n = num; d = 1; return; }
+			if (1 - error < value) { n = num + 1; d = 1; return; }
+
+			int lower_n = 0;
+			int lower_d = 1;
+			int upper_n = 1;
+			int upper_d = 1;
+			while (true) {
+				int middle_n = lower_n + upper_n;
+				int middle_d = lower_d + upper_d;
+
+				if (middle_d * (value + error) < middle_n) {
+					upper_n = middle_n;
+					upper_d = middle_d;
+				}
+				else if (middle_n < (value - error) * middle_d) {
+					lower_n = middle_n;
+					lower_d = middle_d;
+				}
+				else {
+					n = num * middle_d + middle_n;
+					d = middle_d;
+					return;
+				}
+			}
+		}
+	}
+}
diff --git a/Assets/Cryville/Common/Math/FractionUtils.cs.meta b/Assets/Cryville/Common/Math/FractionUtils.cs.meta
new file mode 100644
index 0000000..73b8154
--- /dev/null
+++ b/Assets/Cryville/Common/Math/FractionUtils.cs.meta
@@ -0,0 +1,11 @@
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+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/Assets/Cryville/Crtr/Extensions/Bestdori.meta b/Assets/Cryville/Crtr/Extensions/Bestdori.meta
new file mode 100644
index 0000000..ae4a8db
--- /dev/null
+++ b/Assets/Cryville/Crtr/Extensions/Bestdori.meta
@@ -0,0 +1,8 @@
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diff --git a/Assets/Cryville/Crtr/Extensions/Bestdori/BestdoriChartConverter.cs b/Assets/Cryville/Crtr/Extensions/Bestdori/BestdoriChartConverter.cs
new file mode 100644
index 0000000..6b574ba
--- /dev/null
+++ b/Assets/Cryville/Crtr/Extensions/Bestdori/BestdoriChartConverter.cs
@@ -0,0 +1,183 @@
+using Cryville.Common;
+using Cryville.Common.Math;
+using Cryville.Crtr.Browsing;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json.Linq;
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Cryville.Crtr.Extensions.Bestdori {
+	public class BestdoriChartConverter : ResourceConverter {
+		static readonly string[] SUPPORTED_FORMATS = { ".json" };
+		public override string[] GetSupportedFormats() {
+			return SUPPORTED_FORMATS;
+		}
+
+		public override IEnumerable<Resource> ConvertFrom(FileInfo file) {
+			List<Resource> result = new List<Resource>();
+			List<BestdoriChartEvent> src;
+			using (var reader = new StreamReader(file.FullName)) {
+				src = JsonConvert.DeserializeObject<List<BestdoriChartEvent>>(reader.ReadToEnd());
+			}
+			var group = new Chart.Group() {
+				tracks = new List<Chart.Track>(),
+				notes = new List<Chart.Note>(),
+				motions = new List<Chart.Motion>(),
+			};
+			Chart chart = new Chart {
+				format = 2,
+				time = new BeatTime(0, 0, 1),
+				ruleset = "bang_dream_girls_band_party",
+				sigs = new List<Chart.Signature>(),
+				sounds = new List<Chart.Sound>(),
+				motions = new List<Chart.Motion>(),
+				groups = new List<Chart.Group> { group },
+			};
+			string bgm = null;
+			double? cbpm = null;
+			double pbeat = 0, ctime = 0;
+			double endbeat = 0;
+			foreach (var ev in src) {
+				double cbeat = ev.StartBeat;
+				ctime += cbpm == null ? 0 : (cbeat - pbeat) / cbpm.Value * 60;
+				pbeat = cbeat;
+				if (cbeat > endbeat) endbeat = cbeat;
+				if (ev is BestdoriChartEvent.System) {
+					if (bgm != null) continue;
+					var tev = (BestdoriChartEvent.System)ev;
+					bgm = StringUtils.TrimExt(tev.data);
+					var name = "bang_dream_girls_band_party__" + bgm;
+					result.Add(new SongResource(name, new FileInfo(Path.Combine(file.Directory.FullName, tev.data))));
+					chart.sounds.Add(new Chart.Sound { time = ToBeatTime(tev.beat), id = name });
+				}
+				else if (ev is BestdoriChartEvent.BPM) {
+					var tev = (BestdoriChartEvent.BPM)ev;
+					cbpm = tev.bpm;
+					chart.sigs.Add(new Chart.Signature { time = ToBeatTime(tev.beat), tempo = (float)tev.bpm });
+				}
+				else if (ev is BestdoriChartEvent.Single) {
+					var tev = (BestdoriChartEvent.Single)ev;
+					group.notes.Add(new Chart.Note {
+						time = ToBeatTime(tev.beat),
+						judges = new List<Chart.Judge> { new Chart.Judge { name = tev.flick ? "single_flick" : "single" } },
+						motions = new List<Chart.Motion> { new Chart.Motion { motion = "track:" + tev.lane.ToString() } },
+					});
+				}
+				else if (ev is BestdoriChartEvent.Long) {
+					var tev = (BestdoriChartEvent.Long)ev;
+					var c1 = tev.connections[tev.connections.Count - 1];
+					var note = new Chart.Note {
+						time = ToBeatTime(tev.connections[0].beat),
+						endtime = ToBeatTime(c1.beat),
+						judges = new List<Chart.Judge>(),
+					};
+					for (int i = 0; i < tev.connections.Count; i++) {
+						BestdoriChartEvent.Connection c = tev.connections[i];
+						note.motions.Add(new Chart.Motion { motion = "track:" + c.lane.ToString() });
+						if (i == 0)
+							note.judges.Add(new Chart.Judge { name = "single" });
+						else if (i == tev.connections.Count - 1)
+							note.judges.Add(new Chart.Judge { time = ToBeatTime(c.beat), name = c.flick ? "longend_flick" : "longend" });
+						else if (!c.hidden)
+							note.judges.Add(new Chart.Judge { time = ToBeatTime(c.beat), name = "longnode" });
+					}
+					if (c1.beat > endbeat) endbeat = c1.beat;
+					group.notes.Add(note);
+				}
+				else throw new NotImplementedException("Unsupported event: " + ev.type);
+			}
+			if (bgm == null) throw new FormatException("Chart contains no song");
+			chart.endtime = ToBeatTime(endbeat);
+			result.Add(new RawChartResource(string.Format("bang_dream_girls_band_party__{0}__{1}", bgm, StringUtils.TrimExt(file.Name)), chart, new ChartMeta {
+				name = string.Format("Bandori {0} {1}", bgm, StringUtils.TrimExt(file.Name)),
+				author = "©BanG Dream! Project ©Craft Egg Inc. ©bushiroad",
+				ruleset = "bang_dream_girls_band_party",
+				note_count = group.notes.Count,
+				length = (float)ctime,
+				song = new SongMetaInfo {
+					name = bgm,
+					author = "©BanG Dream! Project ©Craft Egg Inc. ©bushiroad",
+				}
+			}));
+			return result;
+		}
+
+		BeatTime ToBeatTime(double beat, double error = 1e-4) {
+			int i, n, d;
+			FractionUtils.ToFraction(beat, error, out n, out d);
+			i = n / d; n %= d;
+			return new BeatTime(i, n, d);
+		}
+	}
+
+#pragma warning disable IDE1006
+	[JsonConverter(typeof(BestdoriChartEventCreator))]
+	abstract class BestdoriChartEvent {
+		public abstract string type { get; }
+		public abstract double StartBeat { get; }
+		public abstract class InstantEvent : BestdoriChartEvent {
+			public double beat;
+			public override double StartBeat { get { return beat; } }
+		}
+		public class BPM : InstantEvent {
+			public override string type { get { return "BPM"; } }
+			public double bpm;
+		}
+		public class System : InstantEvent {
+			public override string type { get { return "System"; } }
+			public string data;
+		}
+		public abstract class SingleBase : InstantEvent {
+			public double lane;
+			public bool skill;
+			public bool flick;
+		}
+		public class Single : SingleBase {
+			public override string type { get { return "Single"; } }
+		}
+		public class Directional : SingleBase {
+			public override string type { get { return "Directional"; } }
+			public string direction;
+			public int width;
+		}
+		public class Connection : SingleBase {
+			public override string type { get { return null; } }
+			public bool hidden;
+		}
+		public class Long : BestdoriChartEvent {
+			public override string type { get { return "Long"; } }
+			public List<Connection> connections;
+			public override double StartBeat { get { return connections[0].beat; } }
+		}
+		public class Slide : Long {
+			public override string type { get { return "Slide"; } }
+		}
+	}
+#pragma warning restore IDE1006
+	class BestdoriChartEventCreator : CustomCreationConverter<BestdoriChartEvent> {
+		string _currentType;
+
+		public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) {
+			var obj = JObject.ReadFrom(reader);
+			var type = obj["type"];
+			if (type == null) _currentType = null;
+			else _currentType = obj["type"].ToObject<string>();
+			return base.ReadJson(obj.CreateReader(), objectType, existingValue, serializer);
+		}
+
+		public override BestdoriChartEvent Create(Type objectType) {
+			switch (_currentType) {
+				case "BPM": return new BestdoriChartEvent.BPM();
+				case "System": return new BestdoriChartEvent.System();
+				case "Single": return new BestdoriChartEvent.Single();
+				case "Directional": return new BestdoriChartEvent.Directional();
+				case null: return new BestdoriChartEvent.Connection();
+				case "Long": return new BestdoriChartEvent.Long();
+				case "Slide": return new BestdoriChartEvent.Slide();
+				default: throw new ArgumentException("Unknown event type: " + _currentType);
+			}
+		}
+	}
+}
diff --git a/Assets/Cryville/Crtr/Extensions/Bestdori/BestdoriChartConverter.cs.meta b/Assets/Cryville/Crtr/Extensions/Bestdori/BestdoriChartConverter.cs.meta
new file mode 100644
index 0000000..4ce9e63
--- /dev/null
+++ b/Assets/Cryville/Crtr/Extensions/Bestdori/BestdoriChartConverter.cs.meta
@@ -0,0 +1,11 @@
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