Miyako is an idol and a composer at the same time. She debuted near the same time Quartet Night did, but she knew each of them prior to the group debut, meeting each during separate times in her life. She, as an upperclassmen, is assigned as the mentor of Haruka Nanami. As she passes her days with her closest friends, the members of Quartet Night, her underclassmen Haruka Nanami, and the STARISH members, Haruka and the STARISH members start to find out about Miyako's secret past. In the meantime, Miyako and Reiji, Ranmaru, Ai and Camus's relationship continues to evolve. What will happen if "friendship" turns into "love" in the strictly love-forbidden environment?