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 real estate agent, Shinji Sawaguchi finds a fallen meteorite by accident. On the next day, his missing sister Shiori shows up for the first time in ten years. Shinji can't help being agitated by her sudden return. On the other hand, unusual events start happening in his life, and her threatening melody spreads in the town. Including Shinji's fiancé Maki, the development of characters centers around Shiori's mysterious presence felt. Shiori's identity is hidden, and Shinji gets involved in a peculiar situation.

In 2020, the world is forced into lockdown by the COVID pandemic. As remote work is popularized in order to keep the infection rate under control, a young man employed by a company in Tokyo moves to a country town on the Sanriku Coast in Miyagi Prefecture, where he could enjoy fishing, in search of a new lifestyle. But gradually, we found that there were problems such as "empty houses" in the local area.

A man trapped in an endless sterile subway passageway sets out to find Exit 8. The rules of his quest are simple: do not overlook anything out of the ordinary. If you discover an anomaly, turn back immediately. If you don’t, carry on. Then leave from Exit 8. But even a single oversight will send him back to the beginning. Will he ever reach his goal and escape this infinite corridor?