Oz is set in a post-apocalyptic near-future, following World War III. Much of the world has been reduced to desert. The surviving population has fragmented into many nations, and they're all fighting over the planet's declining resources. The only hope seems to be the legendary Oz, a lost laboratory founded by eminent scientists. Filicia Epstein, the surviving daughter of a family of prominent scientists, sets out with a mercenary named Yo Muto on a quest to find Oz and, she hopes, her missing brother Lyon, who is rumored to be there. Filicia and Muto get a lot more than they bargained for.