ROYD-173 "Big sister will teach you all kinds of things ♪" My exclusive tutor sist

Even though my parents are at home, my sister-in-law creates a situation where we are alone under the pretext of helping me study. Then, whether to motivate me or because she is frustrated, she starts whispering dirty words in my ear! She shows me her true nature, which is unimaginable from her appearance, and violates my whole body as if she is enjoying my reaction! Her actions gradually escalate, and I come again and again! Thanks to her, my grades are not improving, and it feels like my brain is being sucked out every day because of my suddenly appointed personal tutor!