Sasakura Ryuu is a college student who authors a particularly bloody series of light novels. One day, he meets a mysterious boy named Mikato. Since "Mikato" is also a character in Ryuu's novels -- not to mention one he's been planning to kill off in the next installment of his story -- Ryuu begins to question himself about what, if any, responsibility he has towards his fans and how they might influence his work.
These questions only grow more pressing and difficult to answer when a string of murders that blatantly copy his novels begins to take place. Worse yet, a "fan" who might well be the perpetrator has taken to sending him 'updates' in the form of photo texts...
(Adapted from [tethysdust]'s synopsis at MangaHelpers