When Kanzaki receives a letter from Mari Setogaya asking to meet in their school's PE storage room during the lunch break, he believes he will be receiving a love confession. He turns up eagerly, only to be attacked by his supposed admirer. The beautiful girl tries to knock him unconscious, but when she fails miserably, she explains that she is a vampire and had wanted to feed on him. Feeling pity, Kanzaki reluctantly allows her to drink his blood.

As it turns out, Mari can't stand the taste of raw blood, but will perish without the nutrients it contains. Kanzaki is quick to find a solution, offering her a different body fluid to consume—and Setogaya instantly falls head over heels with this new flavor...