The Old Era was the time before nuclear contamination. But one day, the nation of Japan released contaminated nuclear wastewater into the ocean, triggering mutations in the marine ecosystem and creating countless mutated creatures, later known collectively as "Beasts." The period after the nuclear contamination came to be called the "Nuclear Era." Human lifespans shrank dramatically, and the world was filled with radiation. Yet newborns miraculously became immune to vast amounts of radiation and could even absorb it to grow stronger. The survivors came to be called the "New Humans," and they gained the strength to fight the Beasts. A New Era began. Beyond the world lay the Radiation Rift, where people could obtain equipment and learn methods for harnessing nuclear radiation. Those who possessed this power were called Nuclear Warriors, also known as Physical Warriors and Spell Warriors. They were the strongest of the New Humans and the main force fighting the Beasts.
