Your girl has been kidnapped, and obviously it is up to you rescue her, punching, kicking and throwing anybody who gets in your way, while building up for the final match.
This is a fighting game, a side-scrolling one where you advance while a series of enemies comes towards you to be beaten to a pulp, and you do not need to do this alone, as a friend can be with you, adding fun, and danger as you can hit each other. But it is not in the fighting itself where the novelty lies. You techniques are just punching, kicking, grabing unconscious enemies or weapons and jumping, all of this while finding more powerful enemies as you advance. All this is as usual.