Believe the Rainbow is an original song composed by Shoichiro Hirata with lyrics and vocals by Sana (Sanae Shintani), serving as the de facto ending theme of maimai FiNALE, and by extension, the classic maimai arcade series. Added on May 10, 2019 as part of the PANDORA BOXXX campaign, the track was originally presented as an extra-extra stage after clearing PANDORA PARADOXXX Re:MASTER, accompanied by a chibi-animated music video bearing the message "Thank you for everything." The song's title had appeared in FiNALE promotional materials before its in-game debut, building anticipation among players. Musically, Believe the Rainbow is a bright, mid-tempo pop track at 133 BPM. Its lyrics weave together the color names of every major maimai version, MURASAKi, BLUE, Orange, GreeN, PiNK, MiLK, and Rainbow, into a narrative about hope and new beginnings, mirroring the song's real-world role as a sendoff to the original maimai hardware line. The phrase "七色のRAINBOW" (seven-colored rainbow) is sung to the melody "so-do-re-mi-fa-mi-re-do," a motif that later resurfaces in other maimai compositions. Both Hirata and Sana were longtime contributors to Konami's BEMANI series before joining the maimai roster. Believe the Rainbow marks Sana's first appearance in a non-BEMANI rhythm game, and the first collaboration between the two artists since "真夏の花・真夏の夢" in beatmania IIDX 9th Style. Hirata had not contributed a new original song to maimai since MIRROR of MAGIC four years prior. The song's Standard MASTER chart (designed by はっぴー) is notable for containing zero HOLD notes, the only standard-format chart in maimai with that distinction, and the highest proportion of SLIDE notes (54.38%) among standard-format charts. Its DX MASTER chart, added in maimai でらっくす PRiSM PLUS and designed by チャン@DP皆伝, functions as a nostalgic medley by quoting short patterns from over 20 previous maimai charts spanning the entire series chronology.