The protagonist of the story is a person who was reincarnated from modern-day Japan to a different world of swords and magic, and over the course of 400 years, he have honed his martial and magical skills, eventually rising up to become the strongest dark knight of the demon army. The protagonist is tasked with protecting the demon realm from human invasions. Despite having this important duty, the protagonist also has a source of “enjoyment” that he look forward to after work. However, due to the recent unsettling movements of the human realm, this source of enjoyment is slowly being taken away from him. To protect his time of relaxation, the protagonist draws his “demonic sword”. The story is a dark fantasy filled with conspiracies, hatred, and battles. It’s a war chronicle where the characters of demons and humans collide with their own individual stories, unfolding in a grand, epic style.