Bungo and Alchemist -Gears of Judgement-

That man decapitates. Inside "Under the Blossoming Cherry Trees," fearing loneliness, the man takes the form of a nameless bandit, hunting for heads as his woman desires. In order to properly complete the story and exterminate the taints, two writers who delve to save him decide to take action to forcibly move the tale forward. Meanwhile, in the library, a certain writer thinks about delving into the book, feeling partially responsible for the man being trapped inside... (Source: Bungou to Alchemist Wiki)