Karneval aimed at being both light and fluffy, with agents who dress up as adorable mascots to make children smile and who play hide-and-seek to keep their charges occupied, and dark, with eyeball-removing serial killers and ordinary people having to be hunted down because they unknowingly have become Varuga.

It was the dumbest thing, and also illustrated the issues this series had with tone. After Circus completes an operation, they put on a show (like a real circus) for the local townspeople as an apology for scaring everyone, and somehow this makes everything better. There are Peacekeepers, who look into minor crimes, and Circus, which supposedly investigates both more major crimes, like murder, and hunts down Varuga, humans or animals that have been genetically altered to have special powers. The world-building is weird and nonsensical. Now that I've read this omnibus (which collects the first couple volumes of the series), I can agree that this series isn't really worth my time and money. I've wanted to try this series for a while, but I vaguely remembered hearing less than positive things about it. When they do eventually get in touch with Circus, there's no Karoku, but a little investigation results in some shocking revelations about Nai's identity. Unfortunately, Nai is a bit stupid and requires constant supervision. Gareki figures that Karoku must be a member of Circus, so he focuses on getting Nai to them. Karoku is an important person to Nai, and he badly wants to find him again. Nai, meanwhile, would happily give it to him but wants to ask permission from its owner first, someone named Karoku. He helps Nai escape in the hope of getting his bracelet and selling it. The leader of the group, Gareki, sees Nai's bracelet and recognizes it as something valuable - it's the ID used by Circus, a special group devoted to hunting Varuga.

They're interrupted by the arrival of a small band of thieves.

This starts with a child-like teen (young man?) named Nai being handed over to Lady Mine, possibly for sex but more likely for food (or, you know, both).

Karneval, Vol. 1 by Touya Mikanagi