Shingeki no Bahamut: Genesis

Thousands of years ago, the dragon Bahamut nearly destroyed Mistarcia until gods and demons joined forces to seal it away and split the key between them. In the present, bounty hunter Favaro Leone lives for himself while avoiding Kaisar Lidfard, who blames him for his family's fall. Favaro's carefree routine ends when a mysterious woman named Amira asks him to guide her to Helheim. He does not realize that she carries half of Bahamut's key. A personal chase suddenly becomes part of a struggle among gods, demons, and humans, all seeking the same power for different reasons, while one mistake could release the creature everyone once feared.