Reborn as a Demon King, I Use Magic to Develop a Star Destroyer!

After transmigrating, Roy discovers that he has become the Supreme Demon King, slain by the Hero a thousand years ago.

Unaware that he is now the strongest being in the plane, he prepares for the dangers of this other world and the possible threat of a Hero.

By day,

he follows Bone Lord's example, disguising himself as an adventurer and blending in with the human empire to gather information,

while also solving countless problems and threats along the way, even earning a noble title.

By night,

he returns to the Demon King's castle to oversee its development,

welcoming all the lowly races, promoting literacy, developing steam engines, researching magical firearms, building a magical internet, and even creating professions like food delivery and taxi services.

At last, when humanity sees the Star Destroyer floating above the Great Demon Kingdom, everyone panics.

The Human Empire Alliance finally decides, "Looks like our only choice is to send the empire's strongest warrior, Count Roy, to lead the troops against the Demon King!"

Roy: ?

This novel and its characters are entirely fictional. Any resemblance to actual people or events is purely coincidental. Do not imitate.