星空パーティーチューン (Hoshizora Party Tune) is a maimai original song contributed by OSTER project featuring vocalist そらこ (Sorako), released for maimai でらっくす UNiVERSE PLUS on June 24, 2022. Clocking in at a brisk 230 BPM, the track captures the exhilaration of live performance, a theme reinforced by its in-game flavor text, which follows a girl named Mika as she steps onto a spotlighted stage, overcomes her stage fright, and finds her voice through music. The lyrics, written by OSTER project themselves, describe linking phrases together like constellations in the night sky, weaving a "party tune" that celebrates the joy of singing and connecting with others. The accompanying movie was created by illustrator 和泉つばす (Izumi Tsubasu), whose visuals bring the song's starry-night stage setting to life. As a maimai original, the song was initially unlockable through Heaven Area 5 (天界ちほー5), and became available by default starting from maimai でらっくす FESTiVAL PLUS. The Expert chart was designed by 翠楼屋 (Suirouya), while the Master chart was handled by はっぴー (Happy), the latter clocking in at level 13+ (13.7) with a dense 939-note layout that leans heavily on Touch notes (93) to complement its driving beat.