The story is inspired from D.Gray Man, Danny the clown is a mysterious one who gave powers to those who need but there is consequences, suddenly he disappeared and then the plague appeared. If you reread it from chapter 1 to the latest, you'll see how the characters are connected to him.
Chapter 1: the girl is the daughter of the "painter" and the woman who died and turned into a leaf
Chapter 2 : the toymaker was the carpenter who claimed himself the master toymaker
Chapter 3: the two men are the people who forced the girl stealing money to provide their broke unemployed lazy ass. A mysterious man hiring them to look for Danny.
Chapter 4: He could be one of the characters who have met and know Danny the clown, maybe it's the black haired kid because he seem to be running an orphanage
Chapter 5 - 15: It's the prequel of how Danny the clown met the people in the past though it only show the black haired kid meeting Danny while others simply said they want to find him and kill him to because they can't accept the consequence of the powers they got from him. Ever since Danny the clown disappeared, the plague appeared with unknown symptoms that turned them into leaves. The kid with strange birthmark is none other than Danny the clown, either he lost his memory or made a deal with the black haired kid.
Super cooooool Supercool... I understand NOTHING