Parenting in the Apocalypse

One day after the zombie apocalypse begins, a four-year-old child appears before a retired middle-aged gangster and an axe-wielding nurse. Ten years after humanity ceased reproducing, the fate of perhaps the last child on Earth rests in the hands of two men who are confident in a fight—but utterly clueless about childcare! Setting out from Busan, the unlikely trio must survive the undead hordes and reach a secret research lab in Seoul.