Fourteen-year-old Chika Hirosuzu is an ordinary middle school girl whose life is turned upside down when a handsome transfer student named Yakumo Sumiyoshi joins her class. After Chika accidentally cuts her finger while showing him around school, Yakumo suddenly licks the blood and promptly proposes marriage. He reveals that he is a vampire bound by a rule: he must marry the first person whose blood he tastes. Worse, he requires a daily dose of either blood or saliva to survive, meaning Chika must kiss him every single day or he will die.

Chika is initially resistant, especially because she wants to save her first kiss for someone she truly loves. Yet Yakumo proves to be exceptionally charming, athletic, and intelligent, quickly becoming the school’s idol. A sports festival becomes the turning point when Yakumo collapses from exhaustion and starvation in the equipment shed. As Chika tends to him, she realizes that Yakumo is actually her childhood friend whom she had long forgotten. From that moment, her feelings begin to shift, and she willingly gives him her first kiss to save his life.

The series follows the sweet, dramatic, and often comedic development of their relationship as they navigate the challenges of a vampire-human romance. Yakumo’s unwavering devotion and his need for daily kisses create a constant source of both embarrassment and deepening affection for Chika. Later arcs introduce romantic rivals, summer trips, and tests of their bond, while successive volume titles such as “2度目のプロポーズ” (The Second Proposal), “3時には甘い口づけを” (A Sweet Kiss at Three), and “5本の指をからめて” (Intertwining Five Fingers) hint at a progression from forced intimacy to genuine love and eventually a more mature commitment. The story maintains a lighthearted, sugary tone as Chika and Yakumo grow closer, culminating in a heartfelt conclusion that celebrates their unique vampire bride and groom relationship.