In the club that Hibiki invited her to, there were already two fixed members. The delinquent bassist Chika and the flutist lady Sakiko. The two of them are from the same middle school and, on the surface, they seem really close, but Chika refers to their relationship with a smile, calling it a 'friends with benefits' situation. Their only commonality is music, but these two share a special past that can no longer be undone...