In a futuristic world where quantum computing reigns supreme, individuals are transferring their consciousness into cyberspace. Remu's gifted sister, Shiki, delves into this digital realm from her high school in the technologically advanced city of OMFC. Through a shocking revelation over Skype, Shiki discloses to Remu that her physical body is submerged in a 'Body Pool,' linked to the cyber network via nanomachines in her brain. Despite Remu's initial acceptance, a catastrophic incident known as 'Early Rupture' unfolds, causing a mass disconnection of minds and leaving vacant shells in the Body Pools. Determined to rescue Shiki's essence, Remu ventures to her OMFC apartment only to encounter a girl claiming to have taken over Shiki's form. As Remu grapples with this unsettling truth, a sudden violent assault disrupts their meeting, plunging them into a tumultuous web of uncertainty and danger.