Masamune Kikuri, a student, discovers a feral girl, Itsumi, in the steel mill blast furnace under the care of his classmate, Mutsumi.

While bonding with Itsumi, Masamune learns conflicting theories about her origins, with Sagami claiming she is a “woman of the gods” and his uncle Tokimune hinting she doesn’t belong in their world.

During a school test of courage, Masamune's classmate Sonobe emits light and vanishes when enveloped by mill smoke, sparking more doubts about the town’s reality.

Through revelations in his father’s diary, Masamune learns Itsumi’s true identity: Saki Kikuri, a girl transported from the real world, and the town itself is a constructed reality.

Reflecting on her past as Itsumi, she visits the steel mill's remnants, where farewell messages and memories of her previous life remain preserved.

Maboroshi is produced by MAPPA, written and directed by Mari Okada, with Yuriko Ishii designing the characters, and Masaru Yokoyama composing the music.