From Apocalypse Boss to Farmer: My Vegetables Make Me Stronger! - Chapter 120 - 111: A Problem That Money Can Solve Is Not a Problem

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

Long Fei, a cross-timer and doujin, is an otaku who traveled to another world. In the original world, he was an otaku fan of Gundam and military science fiction.

He died in an accident and was reincarnated into another world. The Gundam works he had read before his death and the techniques in various military novels could be brought to another world.

How would he use the Gundam that Long Fei created? What waves can be caused in this different world?

A useless prince, yet brimming with kindness and compassion—his smile as warm as sunlight, illuminating this darkened era.But that was merely a mask, hiding the poisonous and mad nature beneath.A monster lurking behind a gentle shell.A system that feeds on stolen Heroines.He will outplay destiny—and rise as the world’s ultimate villain.