Noppo, a spectral entity dwelling within an abandoned apartment complex destined for demolition, appears as an unnaturally tall, pale figure resembling a wraith-like boy, his stature earning him the moniker "Noppo-kun." His existence originates from the building itself, embodying its accumulated history and emotional resonance—a manifestation rooted in Shinto concepts of inanimate objects harboring spiritual essences.

The decaying apartments cradle cherished memories for childhood friends Kosuke and Natsume, who forged bonds within its walls. Noppo remains intrinsically bound to these moments, having silently witnessed their laughter and familial connections over years. His essence intertwines with the structure’s lingering emotional echoes, his desperate yearning to safeguard this vanishing happiness inadvertently propelling the building and its inhabitants into a surreal oceanic void, where forgotten architectures drift as spectral relics.

Noppo’s journey mirrors the tension between preservation and impermanence. Initially, he clings to resurrecting frozen fragments of time, mirroring the building’s defiance against demolition and the children’s unprocessed grief. This resolve wanes as he confronts the impossibility of halting change. In a pivotal act of release, he thrusts Kosuke onto a raft to escape the collapsing limbo, sacrificing his own tether to the past to ensure survival—a gesture symbolizing surrender to progress.

His arc echoes the narrative’s meditation on memory and renewal. By anchoring Kosuke and Natsume’s shared history, including their unresolved guilt over a grandfather’s death, Noppo forces them to confront buried sorrows. His presence catalyzes their emotional reckoning, bridging fractured relationships and guiding them toward acceptance, illustrating liberation through release.