Otokano ~Otouto no Kanojo ga Bunkei de Tsuyome!?~

It’s a summer night. At home. After six months of dating, I finally cross the line with my humanities-major girlfriend. After going at it multiple times, we fall asleep, wrapped in each other’s warmth. The next morning, I wake up to a strange, ticklish sensation between my legs. Blinking away the sleep, I look down to see someone fondling me with a dazed expression. But it’s not my girlfriend— It’s my always-stern, overly-serious, science-major… older sister! [Translated from melonbooks]