Tomohiro, the main character, becomes a sexual friend with his classmate Mina by chance, and they have been in a relationship many times since then, but he never really understands what Mina is thinking. Tomohiro witnesses his girlfriend's junior, Hanashi, masturbating in her library, and ends up having a physical relationship with her and her older sister, Taeko-sensei... A strange love triangle with Mina and Hanaori continues. How will it end? !