[Takashi] Omoide - The Memory (Period) [Black Grimoires]

Momiji's after-school tutoring sessions with an older family acquaintance curdle into nightmare when he finally drops years of pretense, trapping her in his car and taking her virginity while thanking her father for raising such a fine toy. That single violation becomes leverage, and soon her classmates have learned everything—filming her tear-streaked ruin and passing the once-proper student around as their grateful little plaything. A bleak, relentless descent from innocent routine to complete collapse, rendered with cruel attention to every sob and trembling reaction.