Working Undercover in the Kingdom of Heroes as a Demon King

Yang Tianxing is dumbfounded. He's actually a demon king despite having transmigrated into the Kingdom of Heroes.

Turning his back to the Underground World as well as the armies that denounce him, he decides that if you can't beat them, join them.

Three years of hardship is met with another three years.

Yang Tianxing eventually becomes Eternal Continent's United Kingdoms Leader, Holy Prophet of the Church of Light, Sage of the Tower of Truth, Dean of Magic Academy, Emeritus Forgemaster of Ross Cross Society, Heir Apparent of Sword Sage, King of Magical Beasts in the Forest of Thorns, and he receives many other accolades.

At the Peace Prize award-giving ceremony, someone questions him, "Rumor has it that your original identity… is that of a demon king?"
"Nothing but fabrications. I've already handed this to my lawyer."