"Big brother! I'll teach you something naughty just for today!" My slut sister becomes my exclusive sex tutor! ? I have a younger sister who is a bright and kind bimbo even though I am a childish person who is overly negative. As she continued to feel depressed, thinking that she was just a child and nothing good happened to her, her younger sister, who could no longer see me like that...

I'm a shut-in, always observing my younger sister through the peephole in my room. But one day, my younger sister, who was having sex with her boyfriend, started to feel something when we met her eyes...?

The brother and sister who decide everything with the king's game Aoi Shumu