I ended up tutoring my girlfriend’s younger sister, Ruka-chan. Though she’s a high school girl, she’s still very much a child—innocent, cute, and seemingly clueless about sex. She’d carelessly flash her panties or wear see-through bras without realizing… And despite her age, her chest was surprisingly full. Even though I knew she was my girlfriend’s sister, I began seeing her as a “woman.” Before I knew it, I was kissing her soft, youthful lips. Ignoring Ruka-chan’s shocked reaction, I passionately devoured her with my tongue. This was likely her first kiss. Maybe due to her lack of sexual awareness, she didn’t fully grasp the situation. She barely resisted… Just how innocent could she be? The more I realized how despicable my actions were, the harder my penis grew.