A mysterious man in black appears suddenly at a Tokyo hospital, approaching children with incurable diseases and genetic conditions. He offers them healing, and the children are miraculously cured. But the cure has a dark side. The recipients of his treatment quickly become unrecognizable, exhibiting strange shifts in personality and speaking in eerie, ritualistic tones. They begin to herald the arrival of a deity they call Lady Osara, singing songs and displaying unsettling behaviors that disturb their families.

The Sasaki Agency, a small office run by Rumi Sasaki that specializes in paranormal cases, soon receives a flood of similar requests. Rumi is a woman with a difficult past and a unique psychic ability: she can see spirits, monsters, and gods, and she can seal them away inside a mental space she calls the closet. Her assistant, Aoyama, is a kind and gentle young man from a Protestant church family who serves as her moral anchor and her mediator with the outside world. However, when these new cases arrive, Aoyama becomes increasingly distant and unavailable, his behavior growing strange and evasive. Rumi is left to investigate with the help of Katayama, an unnervingly beautiful but morally ambiguous man from her high school days who is fascinated by interesting phenomena.

As Rumi delves deeper, she discovers that the incidents are all connected. The man in black is not a doctor but something far older and more dangerous, tied to local folklore about the moon. The children's recoveries are not blessings but a form of possession, their minds replaced by something that serves the mysterious deity. Rumi must confront the entity behind the healings while also grappling with her growing fear that Aoyama may be involved in the very phenomenon she is trying to stop. The wishes the children made come with a terrible price, and the prayers of desperate parents begin to transform into curses that drag everyone into an inescapable nightmare. The narrative explores the nature of faith, the cost of miracles, and the blurred line between sanctity and madness, all leading to a climax that leaves the true nature of Aoyama's intentions and the fate of the possessed children hanging in an ominous and unresolved balance.