Yuki Nee-chan no Kan-nou Gokko.

In his first year at high school, Shin Yuki harbors a secret affection for someone—Yukino Kurose, an older, book-loving classmate with a captivating figure. Unbeknownst to him, she harbors a scandalous pastime: recreating steamy scenes from erotic literature through playful role-play. As Shin stumbles upon Yukino's secret, he finds himself entangled in her daring impersonation games... or does he?