18+ Mamoru-kun ni Megami no Shukufuku wo!

Mamoru-kun ni Megami no Shukufuku wo! centers around Mamoru Yoshimura, a high school student who gets accepted into a prestigious school for students endowed with the power of Beatrice due to his high intellect. Right after first entering the school on his first day, he meets the mysterious Ayako Takasu, also known as the Beatrice's Angel of Death, who is a pretty and popular female student whose powers exceed most others. Moments later, Ayako, who has never been known to show a smile, suddenly confesses her strong feelings for Mamoru, despite having never met him before. That same day, he is brought in as a member of the student council as Ayako's side as he becomes involved with the dangers and mysteries related to the power of Beatrice.

(Source: Wikipedia)