BAD∞END∞NIGHT is a collaborative VOCALOID original by producers ひとしずくP (Hitoshizuku-P) and やま△ (Yama), two prolific figures in the Japanese VOCALOID doujin music scene. The track features an all-star cast of eight voicebanks, Hatsune Miku, Kagamine Rin & Len, Megurine Luka, KAITO, MEIKO, GUMI, and Camui Gackpo, trading lines in a theatrical, call-and-response narrative about a guest drawn into a mysterious mansion party that takes a sinister turn. The song was first released on the EXIT TUNES PRESENTS Vocalodream feat. 初音ミク compilation album in 2012 and arrived in maimai PLUS on December 13 of that year, making it one of the earliest VOCALOID tracks in the arcade series. BAD∞END∞NIGHT is the opening chapter in a four-song cycle by Hitoshizuku-P and Yama, continued through Crazy ∞ nighT, Twilight ∞ nighT, and EveR ∞ LastinG ∞ NighT, all of which share recurring melodic motifs and the same dark-fairytale atmosphere. Over the span of maimai's version history, the song's in-game genre classification shifted from VARIETY to niconico, and finally settled on niconico & VOCALOID from maimai PiNK onward, reflecting broader changes in how the game categorized its song library. The song received two distinct jackets across its lifetime: the original artwork used from maimai PLUS through FiNALE, and a newly commissioned illustration introduced with maimai でらっくす, at which point the animated background video was also replaced with a static image of the new art. DX charts arrived over thirteen years after the original debut, added in maimai でらっくす CiRCLE on December 5, 2025, and unlockable via Stamp Cards. The DX MASTER chart, designed by メロンポップ, runs at 204 BPM and is recognized as a high-level stamina challenge with dense note streams and extended slide patterns.