The Dawn of the New World - Chapter 9 - The Adventure Begins!

Immediately after Gu Changge realized he had transgressed into a fantasy world, the world’s protagonist, and fortune’s chosen, vowed to take revenge on him. Envied by all, he not only has the female lead head over heels for him but he’s also treated as a distinguished guest wherever he goes. Fortunately, Gu Changge’s prestige and power are superior to everyone else’s, so shouldn’t it be easy to trample on a mere fortune’s chosen?

Transform into Divine Dragon and dominate the world!
He is the only Divine Dragon in the sea who founded an underwater Dragon Palace.
With Crawfish Soldiers and Crab Generals as his followers, wild sharks and gigantic octopuses as his subordinates, he is the dragon that rules the city.

- Description from Novelupdates

When a glorious old civilization was toppled overnight, a strange purple moon rose and thus began the Purple Moon Era.

Saying 5000 year-old-dragon has an impressive ring to it, yet that dragon was an extremely harmless, herbivorous being. However, because of his uselessly giant figure and scary appearance, he was mistaken for the Demon King’s executive and provided by the nearby village with a sacrificial maiden.

Fundamentally cowardly and timid dragon tried to send her away, but the extremely enthusiastic sacrifice didn’t want to give up. Inevitably, he lied: “Okay, I just ate a small portion of your soul, so you can go back already”, but the maiden with outrageous assumptions has misunderstood that she became the dragon’s kin.

Then, out of all things, she began to manifest strange power on the basis of her wrong assumptions – in turn, the helpless dragon, by some mistake started a rebellion against the Demon King.

Rebellion or whatnot, he wasn’t even his subordinate in the first place.