The Abyss Watcher of Kuoh.

Among the great fighters of the old, one name stands above all else, Artorias. One of the vassals of the Morningstar and known to many as the knight wolf. After his fall to the abyss, some of humanity's finest warriors vowed to continue his duty to keep watch of the bottomless Pit. Forming what was called the Abysswatchers. Unfortunately, one by one they too fell to corruption. Until only one family remain, the Kurosakis. Unfortunately, a great fire consume the Kurosaki estate, with his parents nowhere to be found. The only survivor of that fire, Akira was taken by Goro Hyoudou, a friend of his father as a son and begins to live as normal, keeping his true nature a secret even from his new family.

Now in high school, Akira now continues the one thing that keep him going, find his loved ones dead or alive. Unknowlingly entangling himself in a deeper web of the supernatural world.

This story is inspired by "The Devil Abysswalker" authored by @Blackgoku666.