Several centuries into a future where human civilization has declined, a new dominant force known as dragons appeared without warning and steadily reclaimed the world, driving people from their own habitats. To prevent total collapse, a public agency called the Chingochō Futsuryōkyoku Ukeika, or the Vow Section, was established. Its members perform a ritual called the Vow, through which they beseech a dragon to respect the boundaries of human territory and refrain from advancing further.

The story follows two Vow Section officers, Itsuki and Kayano, and their partner dragon, Hachi. Together they travel across Japan, acting as mediators between dragons and the people whose lives are upended by these immense, often merciless beings. In each region they encounter a variety of crises: some dragons are simply expanding their domain, others react to human encroachment, and still more are provoked by deliberate sabotage. Along the way, the pair meet humans who struggle to survive in the shadow of dragons, some cooperating with them cunningly, others opposing them outright.

After an initial series of missions, Itsuki, Kayano, and Hachi return to the agency’s home base, the island of Hōbu, to file reports. On this island, dragons are a familiar presence and the relationship between species is more intimate. Here, secrets about Itsuki’s own body begin to surface, offering hints about his past and the true nature of the bond between humans and dragons.

Later, the team embarks on another nationwide assignment. They encounter an eccentric man who races through the wilderness inspecting ancient ruins, and a dragon that lives alongside humans without a formal Vow, helping them in daily life. These encounters reveal the many shades of coexistence between the two species.

As the story progresses, a colleague of Itsuki’s, Yakumo, and her partner dragon Shirabe are dispatched to a large city where a sudden outbreak of harmful dragon qi is causing devastation. Investigating the source in nearby mountains, Yakumo discovers the remains of a broken seal, clearly tampered with by someone. Following the trail of the culprit, she comes face to face with a figure who appears to be deliberately releasing dangerous dragons. Meanwhile, Itsuki, Kayano, and Hachi confront a dragon that threatens human territory with unmistakable rage, forcing them to face the reality that not all dragons can be reasoned with.