Crossover: The Great Collapse of the Despair King

Blurb:

The King of Despair is one of Xiao Hei's personalities, but he is not Xiao Hei.

The King of Despair is both mad and rational.

"This world, which calls a child the King of Despair, is truly a sorrowful place."

One day, the King of Despair discovered that he had become an individual in his own right and had arrived in other worlds.

The King of Despair smiled, utterly unhinged. He smoothed his hair, put on his glasses to disguise himself as Xiao Hei, and wandered from place to place.

He crossed paths with a female King Arthur and accidentally angered a certain golden-haired king.

He also picked fights with the strongest from both a thousand years ago and a thousand years in the future.

When passing through Yokohama, he accidentally burned down a Port Mafia building.

And so on, a list of glorious achievements.

The golden-haired boy was haughty and arrogant, madness in his eyes. "I am Despair."

"Save me from myself, hero!"

"When death forgets you, you become as despairing as I am."

This is called...

The Great Collapse of the King of Despair.

Why has nobody written about the King of Despair!

Fine, Ster will write it!

Pairing undecided, probably no pairing

I don't know much about Despair, having only seen a few videos

Please point out any out-of-character writing! Thank you!

Mind your manners in the comments!

Theme: There is no light in this world, and death is unknown