Hero's Failure Son

Owen Reeden, the son of a hero, was deemed a failure from a young age. Despite his rough childhood, and life in general, he always shot for his dreams, the chance at becoming his own type of hero.
One day, when going out for groceries, Owen encounters a fight between two monsters. One wants to kill him, the other wants to save him. So when he's forced to take a power called Monster King, Owen is given the opportunity to become what he's always wanted, a hero.