The diligent honor student sister, 'Megu.' While studying in her room, her brother came in and started giving her a massage. But his hands became increasingly perverted, and he began groping her breasts. She had zero experience with men. Plus, the easily coerced 'Megu' ended up having sex with her brother! She might be good at studying, but she's clueless about H stuff. Though her heart was pounding, she decided to let her brother teach her everything that feels good!
