Strait Jacket (2007) on Netflix

In the city of Tristan, where advanced technology works side by side with sorcery, people are under constant threat of demon attack. To protect the defenseless citizens, the Magic Administration Office employs skilled warriors known as Tactical Sorcerists. One day, a half-human, half-demon girl named Kapelteta Fernandez introduces Magic Administrator Nelin Seemonz to the reclusive Tactical Sorcerist Layot Steinberg, a crack shot who fights with a powerful humanoid Mold weapon. Despite his incredible skill at defeating demons, Layot is tortured by the sins of his past, and longs only for death.