Mitsuki-chan, who is more interested in naughty things than studying at her age, stays at home all the time and peeks at her masturbating and having sex with her boyfriend. I have an older brother.As usual, my brother sneaked into Mitsuki-chan's room and tried to do it at night, but failed, and after that day, the power relationship was reversed and my brother who became a servant was treated like livestock by her sister. It will fall until it is done ....