My parents got married and I suddenly got a stepbrother, much older than me. I try to get along with him, but he's a reclusive man who lives in his childhood bedroom, and he won't come out. But Kanon I notice that he masturbates with my underwear every night. Kanon is excited by his loser-like appearance, and since she was bullied at her new school, she starts to take out her frustrations on her stepbrother's crotch on a daily basis. Somehow, she sneaks into his locked room and shows off her potential as a devilish slut.