Mutsuki is very much a girl. However, she knew ever since she was a child that a ‘boy’ existed inside of her. Sometimes he would appear to help her, sometimes to trouble her. Her parents soon divorced because of this and she was separated from her dear twin little sister Nanami.
The years passed and there was a new transfer student to Mutsuki’s all girls school at the end of the summer vacation of her first year. It was her long-separated twin Nanami. However, her personality had changed from doting to cool. Mutsuki was worried that Nanami would become outcasted in the class, but she was particularly cold to her.
She heard from her roommate about one of the school’s seven mysteries, the large mirror in the concert hall. She went there and asked the mirror what she should do. At that moment, she was swallowed up by an ‘alternate time’, then reappeared in front of the mirror. There was a bright light and she heard a voice say to her: “I will grant your wish”.
When she came to, she was in her own room. Was it a dream or was it real? She was holding a small mirror in her hand. From that moment on, the relationships between Mutsuki and Nanami, as well as with the girls around them, began to change greatly.