Hikari no Ou takes place in the aftermath of humanity's last conflict. People have contracted a disease that causes them to catch fire when exposed to natural fire, and the planet is covered in a dense black forest. Hunting the deep-forest dwelling dark animals known as Flame Spirits will be the sole secure supply of fuel. Rumors about "The King of Fire Hunters"—someone who would be able to harvest the man-made star, the millennium comet that previously wandered the void—began to circulate recently among the fire hunters. Koushi, a former student in the city, and Touko, a girl raised in a rural, are the main characters of the narrative. The two's chance meeting, which was not intended to occur, will alter the world's future.