I've Made Mistakes in My Mind
Plagued with horrid nightmares, visions and more, Dipper Pines spent most of his childhood being ruthlessly haunted by a cruel demon by the name of Bill Cipher. Of course, no one was ever willing to hear him out, and nobody believed him. Known as the school nut as a result, the other boys didn't take kindly to him and half of that childhood was spent hiding bruises and cuts from scuffles he lost from his worrisome sister.
Eight years later, the year is 1951. Dipper is 25 and hasn't seen the demon since high school. Having gotten some sort of a grip on his psychosis, he's now a published author of a supernatural encyclopedia and is found escaping his old home on a train to find inspiration for his new book idea.
Fate works in mysterious ways, and inspiration seems to find him first.