Takeru Narihira is a lone wolf delinquent who spends his days getting into fights, avoiding friendships, and being captivated by a mysterious girl named Tsukimiya—someone he's only ever seen in his dreams. One day, a sudden accident sends him tumbling off a cliff. When he regains consciousness, he finds himself in Denji Heian-kyou, a futuristic version of the ancient capital, where advanced technology and mysticism coexist. This world is under the protection of the legendary onmyouji, Abe no Seimei—and to Takeru's shock, Tsukimiya is real and living in this very place. Just as he begins to revel in this fated encounter, a deadly black mist known as Yamikaoru descends, bringing forth monstrous beings called Oni. In the chaos, both he and Tsukimiya are killed—only for Takeru to awaken once again in Denji Heian-kyou. Realizing he has somehow slipped through time, Takeru resolves to defy fate. To protect Tsukimiya from her doomed future, he turns to Abe no Seimei to train in the art of onmyou-jutsu. Now, as an onmyouji himself, he must fight to rewrite destiny and uncover the truth behind this strange new world.

Humanity and demonkind have been on bad terms for millennia, resulting in the continent of Leunders being split in two. Although the situation has stabilized between the races, the fragile peace breaks when the new demon king launches a fierce all-out attack. With all of the non-demon nations falling to the violence in under a year, humanity's hope rests in a special squad, led by swordsman Kyle Leonard, that must assassinate the demon king in order to bring an end to the war. During the dangerous mission, Kyle ends up in a clash with the demon king that brings him to the brink of death. As Kyle realizes he has lost everything he wanted to protect, a mysterious gem transports him back in time before the conflict even started! Now with knowledge of future events and a strong desire to save his loved ones, Kyle sets out to become even stronger to prevent the extinction of humanity.

The age of the demons has begun. Dr Faust has foreseen this rise of evil. Unfortunately, he is near death and is unable to personally battle this upcoming threat. Faust entrusts a young boy, Shingo Yamada, to take the responsibility of ridding the Earth of this new evil presence. Faust finds a birthmark on Shingo's forehead that signifies that he is the chosen demon fighter. Faust summons from hell what may be humanity's only hope of surviving: a less than enthusiastic devil named Mephisto rises. After signing a pact in blood to save humankind, Shingo and Mephisto set out to battle the supernatural world.

In the ancient medicine continent, there are thousands of races, and the alchemist is revered. The Yin and Yang Alchemy God Su Beihuang spent all his efforts to refine the divine elixir, but was plotted by the beauty, integrated with the elixir and hidden for a hundred years. A hundred years later, his descendant Su Beitian was humiliated but still resisted tenaciously. He unexpectedly received the inheritance of the Alchemy God and returned with domineering power! Awakening the dual martial arts of ice and fire, practicing alchemy again, and becoming a young hero. As the truth behind his mother's disappearance is investigated, conspiracies gradually emerge. Let’s see Su Beitian go through many disasters, explore the extremes of martial arts, and become the supreme master of alchemy!