“Oppai Momitai” tte Sakendara, Imouto no Tomodachi to Tsukiau Koto ni Narimashita.
『おっぱい揉みたい』って叫んだら、妹の友達と付き合うことになりました。
A boy expresses a desire to touch breasts, and his wish is answered by a girl named Miko-chan. She asks if he would be her boyfriend in exchange for allowing him to touch her. The story follows their affectionate daily interactions as a couple.