Kirishima Ao came across a scene in the city where someone had collapsed.

Remembering the CPR techniques his father had taught him, Ao rushed to the fallen woman and did everything he could to help.

Thanks to his efforts, the woman’s life was saved. The woman’s daughters turned out to be Yuzuki and Hikari Kotobuki, the beautiful twin sisters who were well-known in their class.

Yuzuki and Hikari decided to search for Ao to thank him properly.