In the ultimate battle between humans and demons, the mightiest hero, Gron, perished alongside the Demon Emperor. Five years later, Gron awakens within the demon camp, discovering his soul has been reincarnated into the body of the weakest demon. Unexpectedly, his soul has unleashed the latent power of an ancient snake god—the power of evolution. Once renowned for his fierce justice, what kind of bloody chaos will Gron unleash in this demonic form?