I'm The Devil - Chapter 42: Rhea Tells The Archangels

Tang Sect, the most famous martial arts sect of all. By stealing its most secret teachings to fulfill his dreams, Tang San committed an unforgivable crime. With his ambition attained, he hands his legacy to the sect and throws himself from the fearsome “Hell’s Peak.”

But he could have never imagined that this would reincarnate him in another world, one without magic, martial arts, and grudges. A land where only the mystical souls of battle lay.

The continent of Douluo.

How will Tang San survive in this unknown environment? With a new road to follow, a new legend begins…

- 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?

- Description from novelbuddy

Chang An, capital of Tang, the most powerful empire in the continent. A heaven wrecking massacre shook the city to its core. Amidst the incident, a young boy named Ning Que managed to get away, dug out from a pile of corpses along with a little girl called Sang Sang. Years passed, and since that day the two of them lived together. Together with Sang Sang they both entered the military, with plausible military achievements, they were recommended into the Scholar School, which began their miraculous journey.

Yamagata Tatsumi and his family were traveling in their car when a wild truck smashed into their car. But wait! The MC wasn’t dead yet, his entire family was though. With his entire family dead and relatives abandoning him, the only one remaining by his side was his pet cockatiel. For a year he lived only with his pet, who had been with him since childhood. But finally, her lifespan reached its end and she died in his arms.