KTRA-431 Cum inside the serious flat-chested little sister, Nana Kisaragi

Sister "Nana" is a serious honor student. When she was studying in her room, her older brother came in and gave her a massage, but her hands became more and more naughty and her breasts were fisted... Zero experience with men. On top of that, "Nana", who is weak against pushing, decides to have sex with her brother as it is! Even if I can study, I'm not good at naughty things. Even though I was nervous, I had to ask my brother to teach me all the pleasant things!