Arve Rezzle: Kikaijikake no Yousei-tachi

In a future where quantum computing has advanced significantly, many individuals have transferred their consciousness into cyberspace. A 14-year-old girl, Shiki, has enrolled in a high school on the academic city of Okinotori-island Mega Float City after skipping grades. She reveals to her brother, Remu, that she communicates from cyberspace while her physical body is preserved in a water tank with a culture medium, connected through brain-implanted nanomachines. This system is known as "Body Pool." After an incident called "Early Rupture" causes a server overload, users' minds become trapped in cyberspace while their bodies remain in the pools. Concerned for his sister, Remu travels to her apartment in the city, where he encounters a girl claiming to have taken over Shiki's body. As he investigates, a violent attack occurs at the apartment.