Rosario to Vampire

Synopsis

The beautiful math teacher Ririko Kagome will be giving midterms soon, but Tsukune is falling behind the others and may end up in summer school if he fails the midterms. Tsukune has math tutoring sessions with the girls, and Moka offers her notes for him to study. However, this draws the attention of Ririko, who insists Tsukune be given extra lessons with her instead. Unfortunately, Tsukune's unusual proficiency in math from these lessons comes at the cost of his personality. Moka finds out that Ririko is a lamia who is trying to seduce Tsukune with her serpent body whilst forcing mathematical formulas into his mind. After Ririko attacks Moka, the latter's notes splatter onto the floor, which brings Tsukune back to his senses. After he removes the rosary on Moka's neck, Moka's inner self easily defeats Ririko. The next day, Tsukune manages to pass the midterms, thanks to Moka's notes. Yukari aces her tests, Mizore barely gets by, and Kurumu fails miserably.

(Source: Wikipedia)