Unbeatable Lv. 1

A brief description of the manga Unbeatable Lv. 1:

The raid failed. In a desperate situation, facing the dungeon boss’s self-destruction, Lee Geonwoo is left alone in the boss room due to a teammate’s betrayal. Just when he thought everything was over, he coincidentally obtained a dagger. Afterwards, his life completely changes… He managed to save his life, but not only did his hard-earned level return to 1, -‘Mosquito’ has been caught. -Level has increased. It’s clear that the level has increased, but why does the level remain the same?