ソリッド ("Solid") is a high-energy Touhou Project vocal arrangement by the acclaimed doujin music circle 豚乙女 (Butaotome), featured in maimai でらっくす PLUS. The track reimagines 今宵は飄逸なエゴイスト (Live ver) ～Egoistic Flowers., the battle theme of the Yorigami sisters, Joon and Shion, from the fighting game 東方憑依華 ～ Antinomy of Common Flowers. With ZUN's original composition as its foundation, Butaotome's arranger and lyricist comp reshapes the melody into a driving, frenetic arrange at 222 BPM, while vocalist ranko delivers the lyrics with characteristic energy and clarity. The song originally appeared on Butaotome's 2018 album 大貧民 ("The Great Pauper"). Its title and lyrical content play on the word "solid", a recurring motif contrasting inner strength and substance against surface-level appearances. The chorus revolves around the phrase "計算違い" (miscalculation), questioning whether happiness can be neatly tallied like a score, and asserting that every person is more solid than they look on the outside. The music video, produced by 駿 and ランコの姉, was published on Butaotome's official YouTube channel and features the circle's signature hand-drawn visual style. In maimai, ソリッド was added at the launch of maimai でらっくす PLUS on January 23, 2020, and is available across all regions (Japan, International, USA, and China). Its Master chart, designed by ロシェ@ペンギン (Roshe@Penguin), sits at Level 13 (constant 13.4) with 748 notes, while the Expert chart by はっぴー (Happy) is a Level 10+ (constant 10.6). The in-game achievement tied to the song, titled "計算違い" (Miscalculation), is earned by clearing the song with exactly 1 MISS, a direct nod to the lyric that anchors the track's hook.