Bones

A demon who was hired to be a playmate to Cotton long ago, and through a contract shares his exact growth scheme, which is "no growing". Was tragically banished from Cotton's court for attempted murder, leaving him to fend for himself in the brutal world that guided him to that point in the first place. After countless scars and a hole melted into his face, a chance encounter reunited the pair, and the forgiveness he was given has led to Bones being fiercely loyal to Cotton.

Over the years, Bones has become more or less aware that Cotton actually forgave him because he's very stupid and has no emotional permanency, but he remains fond and loyal all the same.

In Cotton's demon-hunting company, he's the lead hunter, and cleans up any messes left behind by failed missions. He's aware enough that staying the age Cotton is holding them at will affect his decisions, so is very careful and meticulous when it comes to acting on first impulse to avoid the kinds of problems Cotton constantly causes.