[youseidou (Murasan)] My Little Sister Wants to Know [JnTo]

A studious little sister armed with a health textbook decides her curiosity about the human body requires hands-on research, and her big brother never stood a chance. She pounces with eager confidence—plump thighs, soft round belly, and a thick ass on full display as she demands he satisfy her thirst for knowledge, riding him through her first painful, bloody penetration and into breathless pleasure. What begins as an anatomy lesson melts into sloppy french kisses and a promise to do it even rougher, the chubby young heroine discovering that learning feels best with her onii-chan deep inside.