World background: Ember Era, Solaris continent. This is an era where magic was once glorious, but is now ruled by "gray matter technology". Huge gears and pipes swallow up the remaining magic power of the earth, and the sky is always covered with a layer of lead-grey clouds.
Supernatural elements: There is a curse called "Heart Nightmare" in the world. It does not come from the outside world, but is a concrete monster spawned by the five poisons of "greed, anger, ignorance, pride, and suspicion" in the soul. The inner nightmare is invisible, but it can distort the mind, swallow emotions, and eventually turn the host into a walking zombie. The uniqueness of the protagonist is that he can "see" and "cut off" the nightmares of others, but because of this, his own nightmares are far more powerful and real than anyone else's.
Mission: Destruction is followed by rebirth