ouroboros -twin stroke of the end- is a high-energy instrumental boss track co-created by two prolific rhythm-game composers: Cranky (Hiroshi Watanabe) and MASAKI (ZUNTATA). The song originated in GROOVE COASTER 3 EX DREAM PARTY as a commissioned composition for the fourth Tenkaichi Otogesai (天下一音ゲ祭), a cross-rhythm-game competition that united multiple arcade music games under shared challenge songs. It marked MASAKI's first collaborative work for the event, and the original Groove Coaster presentation visually split the performance into Cranky's white-themed segment and MASAKI's blue-themed segment, a dueling dynamic reflected in the "VS" billing. Carried by a driving 188 BPM tempo and entirely devoid of vocals, the track fuses Cranky's melodic electro style with MASAKI's hard-hitting ZUNTATA-influenced sound design. In the years following its debut, ouroboros crossed over into numerous rhythm game platforms including CHUNITHM, ONGEKI, SOUND VOLTEX, Taiko no Tatsujin, and SYNCHRONICA before arriving in maimai. In maimai DX BUDDiES PLUS, ouroboros was added on April 12, 2024 as an unlockable song in the Groove Coaster Area 2 (グルーヴコースターちほー2) event. Its MASTER chart (level 14.5, designed by サファ太) is a dense, touch-note-heavy course with over 1,250 total notes, while the EXPERT chart (level 12.5, designed by Luxizhel) offers a demanding entry point at 717 notes. The song's subtitle "twin stroke of the end-" alludes to its dual-composer structure, two strokes, two artists, one track.