Нана и Каору

Kaoru Sugimura, the main character, is a BDSM enthusiast. One day, his mother takes the revealing costume he bought from a sex shop and gives it to his childhood friend, Nana Chigusa, for safekeeping. Nana becomes intrigued by the costume and decides to try it on, but the lock on the costume gets stuck, and the key is with Kaoru. In exchange for the key, Kaoru forces Nana to pose for him. As a result, Nana discovers that these BDSM activities with Kaoru improve her school performance, and such encounters become a regular occurrence. Note: The first episode is a bonus to the exclusive limited edition of the sixth volume of the manga.