'm curious about things that are more naughty than studying, and I'm interested in Mai-chan who is always staying home and masturbating and taking a boyfriend and peeking out where she is ecstatic I have an older brother. One day, my brother sneaks into Mai-chan's room and fails to crawl on a nightly basis, and the brother who turns into a sister's servant by reversing the power relationship on that day is treated as a butter dog from her sister like a daily routine It will be done ... This brother and this sister!年頃になって勉強よりもエッチな事に興味津々のまいちゃんにはずっと家に引きこもっていてはオナニーしているところや彼氏を連れ込んでエッチしてるところを覗き見してる浪人中の変態の兄がいる。ある日、兄がまいちゃんの部屋に忍び込み日常的に行ってる夜這いに失敗してしまい、その日を境に力関係が逆転して妹の下僕と化した兄は日課のように妹からバター犬扱いされるようになってしまう…この兄にしてこの妹あり!