The story of a certain boy. A few years ago, his parents divorced due to his father's infidelity, and a new mother entered his life—the so-called stepmother. As a result, the protagonist now has two mothers. One is his biological mother, Terasaki Izumi, who gave birth to him and raised him. The other is his stepmother, Otonashi Kaori, who, despite having no blood relation, treats him with kindness. Living under the same roof with these two women, apart from his father Tatsuo, seemed like it would lead to a happy life—but things didn't go as simply as he imagined.