Jacob Bonheur is the ultimate Clouseau who needs a faithful Cato to accompany him on his various exploits. Your Cato is welcome to look however he/she wants to, have whatever name and backstory, the only requirements being these:
Cato is an angel who takes a contract to kill a demon. He/she can do that for whatever reason you like. As soon as the demon is dead, Cato gets all of their money. They're a decently well-off detective, really good price for one demon. The problem, Cato quickly finds out, is that the demon is very very hard to kill. Every time the angel tries an attempt on Jacob's life, it does not go as planned. Jacob complements them on their tenacity and leaves until next time. This is their odd friendship, or enemy thing, wherever you want to go with it.