Sanada Kouichi's childhood friend Mizusawa Mao has returned after living in France for a couple of years. He is surprised to learn that, since her parents are remaining overseas for the time being, his mother has agreed to let Mao stay with them. Although he has always simply thought of her as a friend, he must now deal with his awakening feelings for her, as well as the feelings he has for his high school crush, Hoshino Yumi.