A masked man disrupts a peaceful afternoon, stabbing everyone in sight. The police later find the suspect dead, making it an open-and-shut case. However, Detective Soma has his misgivings when Shuji, the lone survivor, gets attacked again. Told to survive just ten more days by a mysterious man, Shuji is forced to depend on Soma as they are pushed into a shadowy world neither are prepared for.

Nine days before the mass stabbing, Nakasako's accomplice, Mazaki, settles into a hotel to begin his plans. However, a theft throws everything awry, leading him and a couple of innocent hotel employees down a deadly path. In the present, Shuji accidentally finds a clue that leads to the identity of the mysterious man.