HODV-20766 Don't tell anyone Mari Kobayashi

I insert my dirty soul deep into the girl's secret hole... The secret play of a dangerously hot active rota. A prank only the two of us can do that we can't tell anyone about. With my brother and the recorder, with my teacher after school, with my dad in an empty office... A much-talked-about work that shows the charm of our little sister, Mari Kobayashi.