Diagnosed with dementia, Yuriko's mind quickly begins to fade. Yet, for her son Izumi, memories of the mother feel as vivid as when he lived them. One in particular, when he believed she had disappeared, haunts him terribly.

A man gets lost in an underground passage. He follows the "guide" through the passage, but one after another, strange things happen to him. Is this space real? Or an illusion? Will the man be able to escape the passage?