In the Underworld, I, the Emperor, Am Forced to Live in the Human World.

The underworld is too empty, and my generation of emperors is forced to join the world to work! What, you, a thousand-year-old monster, are still alive in this world? Get it you! What, you have been hiding from the world for thousands of years? Get it you! All the fairies, demons, gods, ghosts and spirits, please handcuff them all away to expand my underworld! This is the advent of an era, and it is also a myth with the emperor!