Nana to Kaoru

Kaoru, a 17-year-old virgin with an interest in BDSM, dreams of sharing an BDSM relationship with his childhood friend, Nana. His mother decides to hide his BDSM toys so he will focus on studying, and asks Nana to keep them out of sight. While looking through the toys, Nana finds a leather one-piece Kaoru bought and tries it on. She accidentally locks herself inside it, but the key is nowhere to be found.