In the year 20XX, a swarm of engineered super-zombies have covered the entire world. But even this cannot deter Aya's determination to track down her father's killer. With sword in hand and wearing nothing but her trademark bikini and cowboy hat, she sets off to settle the score. Aya is joined on her path to vengeance by the chubby Katsuji and the gun-toting Reika. Together, they hack, slash, shoot and bounce their way through a sea of the undead to reach the final showdown with a mad scientist and Aya's fated duel with her own sister.