She is best known as a member of the Konami-produced Japanese teen pop girl group BeForU.
[5] True... was a success in the DDR community, and Kosaka continued to release other songs for use in Bemani both with BeForU and as a solo singer.
While they continued to make music for Konami, BeForU began to put more emphasis on themselves as legitimate musicians, and this included Kosaka.
A year later, she released Riyu Kosaka First Live at O-EAST 2005, a CD+DVD set of her first full-blown concert.
[8] In 2007, Riyu Kosaka recorded a song for the film Kamen Rider The Next, Platinum Smile.
Due to the break-up of BeForU in late 2008, Riyu did not produce any solo works for some time.
In 2021, the song 12 by Naoki and Riyu Kosaka that was in Seven's Code reappears on the game StepManiaX.