My younger brother, who is much older than me, is good at sports and good looking. He recently got a cute Rin, Rin, and he often brings her over to our house. I'm sure he doesn't mean to show her off. But, I'm not popular with girls, so I can't help but see it as a boast. One day, I witnessed my brother and Rin having sex...I couldn't help but record the scene, and that's how it all began...