The four members, Ken Mai, Ruu Jun, are friends with each other as couples. One day when Mai is away, Ken and Ruu are drinking together, and Ruu suddenly confesses to Ken, “Actually, I like her.'' Although Ken is confused, he is pushed by Ruu's momentum and begins to have a physical relationship with her. During the few days that Mai was away, Ken and Ruu began living together for a short time.