In the Taisho era, a world where humans and ayakashi coexist, a deeply devoted couple live in quiet happiness. The husband, Momozane Yonaga, is a kannagi—a shrine exorcist who deals with supernatural matters. His wife, Hika, is a half-ayakashi who carries a blood-drinking tree within her body. Their nightly physical intimacy is tied to a secret connected to yokai, and it is through this bond that they sustain their love and Hika’s existence.

Hika’s nature makes her a target: the flowers she produces are said to cure any illness, drawing the greed of powerful humans and organized institutions. Yonaga, who dotes on her unconditionally, uses his abilities to protect her from those who would capture and exploit her. Despite the danger, their marriage is one of mutual adoration and trust.

The story traces their past and present. Volume 2 reveals their origin: Hika first met Yonaga when she was fourteen and suffering from an incurable disease. She confessed a wish to experience love before dying, and their relationship grew from that moment. Volume 3 deepens the conflict when a friend of Yonaga’s from the Shrine Bureau, Manri, pressures Hika—offering information about her homeland in exchange for her agreeing to leave Yonaga. Meanwhile, a calamity strikes the island of Sara, forcing the couple to face both external threats and the growing question of whether Hika can ever become fully human to ensure a future with the man she loves.