GANGSTA.

Killing is all Spas has ever known, and he does it without doubt or remorse. Taught to believe he’s ridding the world of monsters, he sees the extermination of the Twilights as a necessary step toward making Ergastulum a safer place. Until the day when he’s forced to confront the horrifying truth that the real monster might be…him. 

(Source: VIZ Media)

One shot that preluded the series Gangsta.

Nicolas and Worick run a handy shop that handles everything from deliveries to killing in the Mafia-controlled city of Ergastulum. One day, a dying girl named Sophia appears at their door with a mysterious request: "Hide me for three years".. 

(Source: Amazon, translated)