Uchi no Otouto Maji de Dekain Dakedo Mi ni Konai?

We follow a Japanese of small size, who because of his complexes has suffered a lot in his youth. However, despite all his complexes and flaws, he has something that his little sister Chiaki has long dreamed of. One day, she decides to organize a sex party for her little brother with her friends Nagisa and Yukiko.