On the night of the summer festival Yura Touya's younger sister confessed to him and stole his first kiss. But the problem is, Touya wasn't sure who she was. The reason is, his younger sister holds three personalities within her, and the four of them were in the midst of a Kagome Game.
Without knowing which personality is his real sister, there is only one way for her to return to being an ordinary girl. That is, to grant the wishes of the other personalities and let them disappear from the world. These girls each shoulder their own individual feelings after the night of the summer festival. One girl wants to perform music, one girl wants to sprint, and the last wants to experience love. Even if they turn out to be a fake personality, they all want to remain themselves until the very end.