Kirishima Ao encounters a collapsed woman on the street. Having learned CPR from his father, Ao rushes to her aid and does everything he can to help. Thanks to his actions, the woman survives—and her daughters turn out to be the strikingly beautiful twin sisters in his class, Kotobuki Yuzuki and Kotobuki Hikari. To express their gratitude, Yuzuki and Hikari begin searching for Ao. "I'll definitely make you fall for me." "I'll make sure you come to like me."