Minoru has spent his life attracting demons, a supernatural sensitivity he has learned to tolerate. One night, he rescues what appears to be a sickly stray dog collapsed near his home, only to discover the creature is actually a demon in disguise. Stripped of his true name and power by Minoru's ancestor, a nun who sealed him long ago, the demon is left a shadow of his former self. This demon, who later takes the name Maru, has finally located Minoru and declares he needs him to regain his strength.

To recover his power, Maru binds Minoru into an unholy pact. The method for feeding is not merely blood but physical intimacy, a transaction that demands their bodies become entwined. What begins as a carnal arrangement soon grows complicated as Maru's touch becomes increasingly possessive and Minoru's emotional defenses begin to wane, allowing an unspoken connection to stir between them. The story is set in Japan during the Taisho Era, a period that lends a dreamlike and slightly old-fashioned atmosphere to the tale of yokai and forbidden bonds.

Minoru is a novelist, though his occupation largely serves as a reason for him to be at home, where he struggles with writer's block. He lives with a zashiki-warashi, a childlike house spirit who is the first to alert Minoru that the disguised demon needs help, and who later serves as an indicator that Maru is not a true threat to the household. Maru is the demon who appears first in a dog-like form before transforming into a handsome man. His initial claim of feeding on Minoru to regain his name slowly reveals itself to be a cover for growing devotion and affection.

The narrative unfolds as Maru moves into Minoru's home. As the pact continues, the transactional nature of their nights gives way to genuine companionship. Maru also fends off the lesser annoyance spirits that have always plagued Minoru, providing a practical benefit to the arrangement. However, the story carries an undercurrent of manipulation, as Maru admits he has been searching for Minoru due to their fated connection. The central conflict revolves around whether their bond is merely a means to an end for the demon to reclaim his power or if it can evolve into something more sincere. The single-volume work concludes as a whirlwind romance where the demon's devotion becomes unmistakable, closing on a note that emphasizes their growing emotional bond over the initial carnal agreement.