Kotone Aizuhara is a male university student with a dedicated interest in boys' love narratives. His life in the human world ended when a truck collision killed him during a visit to acquire BL manga, transporting him to an alternate realm devoid of females and governed by distinct social and metaphysical rules. Upon arrival, he encounters Nagi, a divine serpent entity in human form, who declares Kotone his destined partner. Nagi explains their physical union is necessary for his ascension to a higher draconic state.

Initially, Kotone navigates this dynamic using his extensive familiarity with BL tropes, aiming to maintain emotional distance and avoid the submissive roles he recognizes. This knowledge acts as both a defensive mechanism and a source of internal conflict. However, sustained interactions with Nagi and immersion in this world gradually shift his perspective. His reluctance transforms into acceptance of their partnership, evolving into genuine affection. Their relationship becomes a recognized bond within the realm's societal structure.

Kotone's responsibilities extend beyond his bond with Nagi. He attains the significant status of "Sacred Child," a role carrying spiritual and procreative implications for societal continuity. This position involves confronting challenges, including exposure to insect poison grass that induces a fatal climax condition, requiring careful management and trust in his partner. He also participates in formal "Sacred Child Examinations," demonstrating his integration into the world's frameworks.

His journey intersects with other inhabitants, like Wu, a former yakuza navigating his own relationship with Kagetora. These connections further integrate Kotone into the social fabric and broaden his experiences beyond his initial partnership. His narrative trajectory shows adaptation from an outsider reliant on fictional paradigms to an engaged participant contributing to his adopted world's continuity through both his relationship and designated societal functions.