Kankin Kuiki Level X

Ryouka Tsurumi wakes on Christmas Eve to find her apartment building nearly deserted and the surrounding area under evacuation lockdown. Her mother warns her by phone that an unknown entity called X has appeared nearby and that Ryouka's childhood friend Shuuhei Murosaka is the only other person still inside the building. Ryouka soon learns that X does not hunt alone: it can control people and turn them into predators on its behalf.

Ryouka and Shuuhei try to escape, but their violent deaths do not end the nightmare. Ryouka awakens again in her room at the same starting point, only to face a different X. Once she realizes that death resets time, every failed attempt becomes information she can carry into the next loop. Together with Shuuhei, she begins searching for the one route that can take them both out of the locked zone alive.