A vampire works in a bathhouse in hopes of drinking the virgin blood of its heir Rihito, who worryingly falls in love on his first day of high school.

Ranmaru worries he has inadvertently made Aoi interested in Rihito. Rihito chats with Aoi the next day after school, but they soon get into trouble.

After saving Aoi, a hungry Ranmaru tries to resist the urge to feed on her. Rihito soon arrives at the scene and comes to a mistaken realization.

Franken proclaims his admiration for Ranmaru, who tasks him with protecting Rihito. Franken tags along with them back to the Tatsuno house for dinner.

Rihito's teacher Sakamoto — an undercover vampire hunter of notable lineage — learns that his longtime foe Ranmaru lives with the Tatsunos.

As Sakamoto tells Ranmaru the reason for his unexpected request, a puzzled Rihito walks in on them. Ranmaru reveals how Sakamoto's ancestor died.

At the Koi Bathhouse, Franken and Sakamoto attempt to bring their plan to fruition by urging Rihito to tell Aoi how he feels about her.

Tough girl Kaoru is charmed by Rihito's cuteness, but when she goes to return a handkerchief he lent her, she can't seem to drop her brash attitude.

After a confrontation with Kaoru's father, Ranmaru attempts to drink Kaoru's blood. However, he's repulsed by her makeup — which gives him an idea.

Sakamoto tells Ranmaru he was attacked by a vampire at the school. After a remedial night class, Franken and Kaoru encounter a boyish-looking vampire.

Thoughts of Rihito give Ranmaru strength as he struggles against the formidable Nagayoshi. Suddenly, Kaoru appears with an improvised weapon in hand.

Ranmaru asks Rihito's father to let Nagayoshi stay in the apartment behind the bathhouse. A newly inspired Nagayoshi declares he's in love with Kaoru.