GLAAAAAAAAAAAAAAADDDDDDLLYYY (dang, wut a coincidence XD)
So he's an American boy that grew up in a rich neighborhood and attended a Christian Academy at the age of 12, where he was very popular among the others for his good looks. A few months later, he meets Fusae. He suddenly has a crush on her, but she doesn't like him back (bc of HER tragic bg). So he tries his best to make a good impression on him, and eventually ends up winning her heart 2 months later. They start dating, and a few months later (he turned 13 at this point), on Valentine's day, when they fully express their love to each other, the UHSO (Undercover Hybrid-Scientists Organization) shows up at the school and, because they want Fusae back, burn the Academy down. While Asher and Fusae escape through the flames, a large piece of the building falls from the ceiling above Fusae at a fast rate. To protect her, Asher lunges at her and pushes her out of the way, crushed by the debris.
And that is the day he died.