Cheon Yeo-Woon is an illegitimate successor to a demonic cult, lacking both strength and martial arts skills. While being pursued by assassins sent by one of his rivals, he reaches a point of total despair. At that exact moment, a mysterious man from the future appears and injects a nanomachine into his body.

With this cutting-edge technology now inside him, will he be able to surpass his innate physical limitations, become the strongest, and finally take his place as the second Cheonma—the supreme leader of the demons?