Valkyrie's Shadow - Chapter 16Winter’s Crown: Act 3,

The Demon Empire in the universe was reborn and came back! Enemies should kneel down in front of him! Beauties should lie down in front of him!

“I am a demon. I enslave gods and immortals! If you don’t succumb to me, I will convince you by force!”–Ye Feng!

A boy awakens alone in the Fairy Tail world, lost and uncertain. As he ventures through this magical realm, he unravels the secrets of his mysterious new identity, unlocks hidden powers, and carves out his destiny in a land brimming with wonder, danger, and limitless adventure.“Check out my other work, Reincarnated as Ash: A Pokémon Tale.”

When Song Xiao was young, he wanted to become a Virtuous Official for a lifetime, but was forced to marry into the palace by that uncooperative Emperor; when his Virtuous Empress For A Lifetime career had just started, the Emperor died……

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?

- Description from novelbuddy