Human civilization no longer revolves around fire, but is instead now driven by fear of it. Repeated wars have changed human biology, and people now spontaneously combust when they get close to natural flame. However, a new source of energy prevents society from complete collapse: a stone-shaped material used to produce light and steam lies within the bodies of monsters that infest numerous forests. Those tasked with collecting this precious resource are called fire hunters.

Touko, a young village girl, is saved from a forest monster by a fire hunter who perishes during his heroic action. After the hunter's dog, Kanata, heals from his own injury, the girl's family sends her to the capital in order to return Kanata and the hunter's fire sickle to his relatives.

Elsewhere, the fire hunter's son, Koushi, and his sister are adopted by a wealthy family. Koushi learns some troubling facts related to the country's ruling royal family. He conducts secret research on a special fire stone found by his late father, kickstarting a race against time between the country's leaders and those trying to save mankind from its ultimate demise.