Natsu ga Owaru made The Animation – Episode 1 (ES)

Childhood sweethearts Yui and Kou, now lovers, sneak away for passionate sex in the school clubroom one day. Unbeknownst to them, a sleazy teacher spies the entire encounter and uses it as leverage to blackmail Yui. To keep their relationship and Kou's future safe, she agrees to his demands, allowing him to use her body in exchange for silence. At first, Yui feels nothing but disgust and hatred toward being violated by anyone other than her beloved boyfriend. But as the encounters continue, her resistant mind battles against the growing physical sensations—the teacher's skilled manipulations force waves of unwanted pleasure upon her. Her body betrays her resolve, craving more with each session. Eventually, the depraved instructor claims the final taboo: her virgin anal passage, which she had never even let Kou touch. This upper volume of the animated adaptation captures the slow corruption from reluctant submission to eager indulgence, blending emotional turmoil, blackmail NTR, and intense sexual awakening. A must-watch for fans of school settings, netorare themes, anal training, big breasts, reluctant-to-fallen heroine dynamics, and high-quality motion animation that faithfully recreates the original doujin's erotic tension.