In the cursed village of Inakamura, isolated by a perpetual fog that warps time and memory, the story follows Yuuki Tachibana, a boy branded from birth with the Jūjika—a cross-shaped birthmark that is not a mark of holiness but a beacon for the Jashin, parasitic demons born from human despair. Unlike the villagers who hide their marks and live in fear, Yuuki cannot conceal his. When his mother is taken by a high-ranking Jashin known as The Puppeteer, Yuuki learns the village’s dark secret: the Jashin were created by the villagers’ own ancestors to escape a plague, and now the debt must be paid every generation.

The main conflict begins when Yuuki meets Shiori Amamiya, a shrine maiden from outside the village who has come to seal the Jashin for good. Shiori possesses the Kuchizuke no Ken, a forbidden technique that can destroy a Jashin but requires a kiss of absolute trust with a Jūjika bearer to activate. Their first kiss, born of desperation rather than trust, fails—it burns Yuuki and nearly kills Shiori. From this failure, they learn that the technique only works if the bearer accepts their curse as part of themselves, not something to be removed.

The cast expands to include Kaito Murakami, a cynical bearer who has learned to control his Jashin by making a pact with it, becoming a dangerous neutral party. Reina Hoshino is a bearer who fled the village years ago and now returns as a Jashin hunter, believing the only solution is to kill every marked person to starve the demons. Father Enoki is the village priest who knows the original prayer that created the Jashin but refuses to speak it, believing the demons deserve to exist as punishment for the ancestors’ sins.

The narrative unfolds through notable arcs. The Pact Arc sees Yuuki attempting Kaito’s method of making a deal with his Jashin, which grants him power but begins transforming him into a demon. The Sealing Arc takes Yuuki and Shiori into the Jashin’s dimension, the Fold, where time moves differently and they must face physical manifestations of their worst memories. The Betrayal Arc reveals that Shiori’s order never intended to seal the Jashin—they want to capture the demons for military use, and she is a sleeper agent programmed to betray Yuuki at the moment of the final kiss. The Confession Arc is the emotional climax where Yuuki, now half-transformed, chooses to trust Shiori anyway, and she breaks her programming through sheer will. Their final kiss activates the Kuchizuke no Ken not as a weapon but as a purification, turning the Jashin back into the sorrow they came from.

The story resolves when Yuuki does not destroy the Jashin but instead uses his mark to absorb all of them into himself, becoming a living prison. Shiori seals him inside a new shrine, and the last scene shows her visiting every year, pressing her hand to the stone where his heartbeat can still be felt. The fog lifts from Inakamura, but Yuuki remains inside, bearing the weight of every demon so no one else has to.