Deals And Secrets-Alastor x Reader

Your name is Abigail, and you are 16. Your little brother, Gage, who is 13, went missing two years ago. Everyone who knows him thinks he's dead because he's been gone so long. Everyone except for you. So, you run away from home, in search of your brother.
What you find out is truly shocking.
It involves a demon named Alastor
The Raidio Demon.