Classmate no Okaasan

Jun is in his second year of high school. He loves a female teacher, Keiko, though she is much older than him. He joins a badminton club that Keiko is in charge. Luckily, there is no other club members and he enjoys practicing it with Keiko after school.... One day, a girl talks to him.... It is Keikos daughter, Sae. "My mother talks about you a lot at home." Also, he finds that her husband passed away ten years ago. Triggered by this fact, he makes up his mind to tell Keiko that he loves her....