Japan has become a wasteland devastated by the Rusty Wind which causes all things to rust away. A suspicious looking priest visits a checkpoint all alone, yet on his back rests a bow priests wouldn't use.
Meanwhile, Milo, a doctor running a clinic in the town of Imihama, is researching new medicines in secret in order to save his older sister, Pawoo, who's being corroded by the Rust. But that day a stranger appears before him...
and that even the strongest poisons 
can become the strongest medicine.
وبأنّه حتّى أقوى السّموم يمكن أن تصبح الدّواء الأقوى
so kann starkes Gift
gleichsam starke Medizin sein!
Les meilleurs poisons font
les meilleurs remèdes.
e che persino il più potente dei veleni
può diventare la più efficace delle medicine.
e que os venenos mais fortes se 
tornam os remédios mais fortes.
а значит, сильный яд
станет лучшим лекарством!