When Kanzaki gets a letter from Mari Setogaya requesting a meeting in their school's PE storage room during lunch break, he assumes he is about to receive a love confession. He arrives eagerly, only to be attacked by his supposed admirer. The beautiful girl attempts to knock him unconscious, but when she fails completely, she explains that she is a vampire and had intended to feed on him. Feeling pity for her hopeless situation, Kanzaki reluctantly gives in and lets her drink his blood. It turns out that Mari cannot stand the taste of raw blood but will perish without the nutrients it contains. Kanzaki quickly finds a solution, offering her a different bodily fluid to consume—and Setogaya instantly falls head over heels for this new flavor. The two soon begin meeting regularly, and as time passes, their relationship evolves into something more than just casual "meals" spent together.