Uchi no Otouto Maji de Dekain Dakedo Mi ni Konai

Nao, a boy who was troubled by the fact that his penis was bigger than his short stature. Now, he's having sex with his sister-in-law's friends, Nagisa and Yukiko and his confidence has grown. In the meantime, his sister-in-law Chiaki who is thrilled to see him accepts her brother's forceful advances...?