folern is an original song by Japanese Vocaloid producer and composer ぬゆり (nulut, also romanized as nuyuri), first appearing in SEGA's CHUNITHM AMAZON before being ported to maimai でらっくす UNiVERSE PLUS as part of a CHUNITHM collaboration event. The track is defined by its relentless 200 BPM tempo, a driving electronic arrangement, and vocals performed in a fictional constructed language, a signature touch from nulut that gives the song an otherworldly, incantatory quality. The song has traveled unusually far beyond SEGA's arcade ecosystem, appearing in ONGEKI, Project Sekai: Colorful Stage! feat. Hatsune Miku, and even the 2025 title Like a Dragon: Pirate Yakuza in Hawaii, an exceptionally rare crossover between SEGA's rhythm game catalog and its flagship action-adventure series. A remix by Zekk was also released on the CHU REMIX vol.2 compilation album. The jacket artwork features the CHUNITHM character Silvius (シルヴィアス), whose presence extends into the game's chart design: the CHUNITHM WORLD'S END chart is credited to "Silvius vs Astraea," weaving the character directly into the play experience. In maimai, the MASTER chart at level 13+ (difficulty constant 13.9) was designed by 翠楼屋 (Suirouya), who also handled the EXPERT chart, making it one of the more demanding tracks in the UNiVERSE PLUS era.