Killer Bang: The First Kill

Uigang Bang is an ordinary small business owner who leads an ordinary life… until unordinary things start to unfold in his life. His business partner suddenly disappears, leaving a notorious loan shark chasing after his company. His wife and their child-like dog survive an attempted murder by an impulsive killer only to live in fear of his second attack. Uigang faces the killer to end the matter, but things go south and now he faces two dead bodies instead. Just when he’s debating whether to turn himself in, he receives a life-changing offer -- do you want to become a hitman?

(Source: WEBTOONS)

Note: Chapter count includes Episode 0.