Me too, but just read along and I think it will clear up as it goes
My understanding that that Garan is a demon/god or a praised being created by humans desires and greed. He was originally just a mirror before. He attacked somewhere or caused trouble in the demon world and a co-operation that deals with things of that nature confronted him and he chosw to live with the main character while dealing with the stress of being something he didnt want to be
This sums it well!! ↑↑↑
I'm having a hard time following the story @_@