There are two planes on the dual-source star in a different world. The A plane is a human planet that is very similar to the earth, while the B plane is a demon planet with a harsh environment. Humans and demons in the two planes correspond to each other. A human in the A plane must have a demon in the B plane with the same name. As long as certain conditions are met, humans and demons in the two planes can be converted into each other. Due to the obstruction of the transformed superior demons in the human plane, a world-destroying war broke out on the human planet. Humanity's technology and civilization level returned to the primitive, and cold weapons became mainstream again, but technology still existed in a few places. In this apocalyptic world where the East meets the West and the modern meets the primitive, demons erupt on a large scale to rule mankind. The protagonist Skarner, because of a transformation ceremony for a king-level demon, the village where he lived was destroyed, and then accidentally obtained a strange heavy sword. This is a giant sword that can slowly and infinitely become heavier, and there are other souls residing in this sword, and there is another bigger secret hidden in it.
