In the distant future, a catastrophe called the "Rusty Wind" has turned most of Japan into a barren desert and reduced civilization to ruins. After his teacher succumbs to the rust, the roguish Bisco Akahoshi sets out on a journey through the sandy wastes to find a mushroom known only as the Rust Eater, which is rumored to cure the disease. Alongside the dashing young doctor Milo, the duo must face the harsh environment and other wanderers to survive the trip back.