This repository is a large, structured dataset of maimai rhythm-game charts, not an application. It contains over 1,800 maidata.txt files organized by in-game genre such as POPSアニメ, niconicoボーカロイド, 東方Project, ゲームバラエティ, オンゲキCHUNITHM and 宴会場, plus collection manifests and an index.json song catalog. Every chart file is stamped as produced by MaichartConverter/Neskol v1.0.9.0, and uses the same key/value metadata header followed by per-difficulty &inote_N blocks in a compact note notation that encodes tap positions, holds, slides, break notes, chords, BPM changes and cabinet/version information. The data spans maimai SD through maimai DX PRiSM and beyond, making it a comprehensive cross-version chart corpus. It can serve as ground truth for simulator ingestion, chart format analysis, difficulty prediction, archival, or generation tooling. The chart notation is consistent enough that a parser/lexer could be derived by example from these files, and the stable shortid/artistid/genreid fields allow relational joins with the included index.json and collection manifests. The main weaknesses are the absence of the converter source, a formal schema, validation tooling, or license; a few files contain placeholder values such as artistid=999 or empty difficulty levels. Overall this is a well-curated data asset with high reuse potential for anything that needs maimai chart content, but consumers should treat the format as reverse-engineered rather than officially documented.