BATTLE NO.1 is a collaborative hardcore track produced by 14 DJs from the HARDCORE TANO*C label, united under the pseudonym TANO*C Sound Team. The name deliberately parodies KONAMI's "BEMANI Sound Team" credit, a knowing nod to the song's origin as a rejected submission to the 2019 SOUND VOLTEX The 8th KAC Original Song Contest. Despite that competitive rejection, the track went on to appear in five different rhythm game franchises: maimai, CHUNITHM, オンゲキ, WACCA, and Arcaea. The version featured in maimai incorporates an additional section by Massive New Krew that was first added for the WACCA release, distinguishing it from the original contest submission. The MASTER chart mirrors the track's collaborative spirit: each of the 13 composer segments was assigned a different notes designer, resulting in a 1200-note, 14.5-constant chart that serves as a curated tour through the HARDCORE TANO*C roster's signature styles. It launched at level 14+ before being adjusted to 14 in Splash PLUS. In maimai DX Splash, BATTLE NO.1 was gated behind the game's highest grade, 拾皆伝 (10 Kaiden), requiring players to defeat its dedicated boss friend or receive the song via conduction from another 拾皆伝 player. International versions made the track available by default from the DX PLUS era onward, and it became universally available in Splash PLUS.