A deadly virus is spreading across mankind, turning humans into gruesome monsters known as 'Kanshu'. Yet no one knows of their existence, except for the organization called 'F.L.A.G.', dedicated to hunting down and destroying the source of the infection. Its members possess extraordinary powers, capable of unleashing righteous fury on their enemies. One day, a cell phone message from a dead relative leads estranged youth Riku Amami unwittingly into the conflict between F.L.A.G. and Kanshu - and to a mysterious cocoon that would change his life forever, for better or worse...