‘Gungrave’

Brandon Heat, a silent and passive man, is living a laid back life with his friends. He’s got his eyes on Maria, but her father forbids their relationship. After the brutal murder of his friends and Maria’s father, Brandon is on the run together with the only friend he has left; Harry McDowell. When he finds out custody over Maria has been taken by Millennion, the largest mafia syndicate in town, he and Harry decide to join the syndicate. He goes through many hardships after joining the syndicate but he is willing to risk everything as long as he can be close to Maria.

Descriptions taken from AniDB.net