Derrick is the son of the biggest Hunter guild in England. He talented and strong too. That make the citizen like him when he appears in the tv. When dungeon appear in the world, System also appears to guide the human, to fight monster. But only little of them has humanoid body as they is high level system. Derrick has one as they living together since that is his system. System manage the leveling up of the hunter and the one held inventory for human put something in dungeon later.