Japan is suffering from an overflow of monstrous beings called nightmares. This is the fault of one nightmare in particular: The Worst Nightmare. Kenji Endomoto, a 15 year old boy, is given the opportunity amidst the hectic era and uses the power of the nightmares to fight against the very nightmares themselves. Recently, a serial killer that targets people like Kenji has been gaining a lot of attention to their name. An old friend asks Kenji and the gang for help. After a failed confrontation, the gang realizes that this serial killer is far more dangerous than they expected. Kenji is even more determined when he learns that everyone he cares for are at risk for what awaited this case.