Nagi is a divine serpent beast inhabiting an alternate world without women. He manifests in a half-serpent, half-human form. His core purpose is achieving ascension to a higher dragon state, a transformation requiring sexual union with a human partner destined to be his "Miko." This union is fundamental to his divine nature and role within the world.

Kotone Aizuhara, a human male summoned into this world after his death, becomes the object of Nagi's pursuit. Nagi explicitly states that physical intimacy with Kotone is necessary for his own metamorphosis into a dragon. He asserts his claim over Kotone as his destined bride, defining their relationship through this supernatural imperative.

Nagi exhibits persistent focus on fulfilling this ascension goal. He approaches Kotone with directness, rooted in his perceived divine mandate, viewing the human as essential for his evolution. Information concerning Nagi's origins beyond his divine beast status, detailed personal history, specific vulnerabilities, significant internal conflicts, or substantial shifts in his personality, motivations, or relationship dynamics with Kotone is not elaborated upon.