Ultraman - Only Want To Protect You - Chapter 34

In Heaven’s Vault Continent, Colossal Dragons, Titans, Beast People, Fairies, Magical Beasts, and other races reign supreme!

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

Horror of the Continent: The Immortal King Brings Despair, While the Light Knight Defies the Divine Will.In an era of chaos, numerous heroes emerge, striving to navigate the tumultuous land. However, amidst this turmoil, sudden and enigmatic forces make their appearance on the continent.Little did they know, it was all me.…To be precise, they were my alter egos sent to this other world.#Unintentionally becoming the villain of the world.#Somehow, I become both the demon king and the hero.#One person, multiple roles.

This is an alternate history. Decades after the fall of the Eastern Jin Dynasty, the world is still in chaos, although there is hope for reunification.