Kou Yamori, an average middle schooler grappling with the enigma of love, chooses to skip school as a form of rebellion against societal norms. Adrift in sleeplessness, he wanders the desolate streets at night until a peculiar encounter with Nazuna Nanakusa, a girl who believes insomnia stems from unresolved daily regrets. Nazuna, offering help with his sleep struggles, persuades Kou to share a futon with her, only to shock him by revealing her true nature as a vampire through a bite. Kou, mistaken in his belief of immediate transformation, learns that to become a vampire, he must be bitten by his true love. Resolving to embrace this supernatural destiny, Kou sets out to love Nazuna and join her in the immortal realm.