I hunt mansters?

In the year 2030, humans became victim to a war started by the inhuman creatures called the 'Mansters'. Humanity was slaughtered and forced to live in massive underground vaults for survival. After 3 years, a new threat capable of destroying the world peace arrives yet again. This time around, Earth has a new hero capable of stopping the catastrophe with the only issue that he is still a level 1 'dismantler'.