eufonius [ユーフォニアス] is a group formed in Japan by riya and became famous in the otokei scene by performing original songs, that they presented at conventions such as M3 and Comiket. eufonius is made of two members: ｒｉｙａ, who performs vocals and sometimes composes; Kikuchi Hajime [菊地 創], also known as cuckool, who composes and arranges songs. The group made their major debut (2004) by releasing their maxi single "habataku mirai" [はばたく未来] used as opening theme for the anime "futakoi".