Holy Knight is the story of a young male vampire slayer who reluctantly falls in love with a beautiful female vampire exchange student and their personal struggles to avoid their bloody predestined conflict.

High school sophomore Kusuo Saiki swore as a child that he would keep his psychic talents hidden, but his abilities still make his life difficult.

Iwakura Mitsumi, a tenacious country girl, prepares for high school in the big city. She meets the handsome Shima Sousuke, whose easygoing ways help her adapt in the real world.

Puberty Syndrome—a rumored, mysterious syndrome that only affects those in their puberty. For example, a bunny girl suddenly appeared in front of Sakuta Azusagawa. The bunny girl's real identity is Mai Sakurajima, a teenage celebrity who is currently an inactive high school senior. For some reason, her charming figure does not reflect in the eyes of others. In the course of revealing the mystery behind this phenomenon, Sakuta begins to explore his feelings towards Mai. Set in a city where the skies and seas shine, Sakuta unfolds the meaning behind his bizarre encounters on women with the said syndrome.