アンダーキッズ is a song by the Japanese musical project ツユ (TUYU), released as a self-titled single in 2022 and later added to maimai でらっくす BUDDiES on September 14, 2023. The track is built around a driving, high-tempo arrangement at 225 BPM, with composition, arrangement, and lyrics by Pusu and vocals by Rei, the core creative duo behind TUYU's signature blend of pop melodies and emotionally charged lyricism. The music video was directed by AzyuN and 双葉陽. Lyrically, アンダーキッズ delves into themes of adolescent despair, social alienation, and a defiant rejection of a world the narrator feels abandoned by. Its refrain, 「誰でもいい　嘘でもいいから認めて？」 (Anyone will do, even lies are fine, so acknowledge me?), captures the song's raw plea for recognition from those who feel invisible. The title itself, "Under Kids," evokes the idea of children living beneath society's notice. In maimai, the song arrived as part of the BUDDiES launch lineup and was available for roughly 295 days before being removed from the Japanese version on July 5, 2024 during the BUDDiES PLUS update, and from the Asian version at that update's launch. The Master chart, designed by Luxizhel, is a level 13 (13.4 constant) featuring a notably high Slide-note count of 174, an unusual density for its difficulty tier, alongside heavy Break-note usage. The Expert chart was designed by 翠楼屋 (Suirouya). Internally classified under POPS＆アニメ in maimai and niconico in CHUNITHM (where it also appeared briefly in LUMINOUS), the song had an unusually short lifespan across both arcade rhythm games.