[Slow-burning group portrait, light novel]
The clean energy R particles developed by humans mutated into RX particles.
A hundred years later, animals and plants (monsters) infected by RX particles roamed the wild, and the earth became no longer suitable for survival. Human beings in desperate situation discovered the "Watch Tower Stand" and established a group of sentry towers to block the spread of RX particles, which they called: "The Circle". Human civilization can continue within the "circle". Also created at the same time was the battle armor, a weapon used to fight monsters.
On the other hand, the world outside the "circle" is ruled by the Demon King and his men. For hundreds of years, they have been waiting for the resurrection of the Demon King's soul while coveting the civilization within the circle.
The story begins in Circle No. 0037. In Circle No. 0037, There is a group of boys and girls who, in order to protect their hometown and important people, have no fear when facing monsters and grow into excellent demon hunters.
