On her way to school, Eriko is captivated by a beautiful, idol-like girl who picks up her dropped handkerchief. That day's swimming lesson is held at the nearby Shimomura Junior High School pool, as the swimming pool is out of order. After the lesson ends safely, as Eriko and her friends are about to return to Sakijo, a student from Shimomura Junior High approaches them. It is the beautiful girl Eriko met that morning...!