Borderline, tome 1

The weakest of the weak, E-class hunter Jinwoo Sung has no money, no talent, and no prospects to speak of. And when he enters a hidden dungeon that fateful day, he ends up being left to die in the aftermath of a horrendous tragedy. At death's door, Jinwoo is suddenly invited to be a "player" by a mysterious voice. Desperate to live, Jinwoo jumps at the chance...but what is this strange new leveling system that only he can see?