SONE-681 "Too innocent, being led around by an older man!?" Her younger sister made me lustful, and I secretly kept having sex with her. The worst kind of guy is me. Ito Ruka

I ended up teaching my girlfriend's younger sister, Ruka-chan, her studies. Even though she's a female student, she's still just a kid, innocent and cute. She seems to know little about sex, carelessly flashing her panties or wearing see-through bras... Plus, for her age, her chest is quite developed. Even knowing she's my girlfriend's sister, I can't help but see her as a 'woman.' Before I knew it, I was kissing her soft, young lips. Ruka-chan looked surprised, but I was lost in the moment, greedily devouring her tongue with mine. It was probably her first kiss. Due to her lack of sexual knowledge, she seems not to fully grasp the situation yet. She doesn't seem to mind... Is she really this innocent? I'm aware of how low my actions are, but my penis is already erect.