Time Reaper: Rise Of The Blood Monarch - Chapter 17: Going Home.

In the post-apocalyptic age, men were damned.

An engagement paper to lock one’s destiny. With her family facing financial difficulties, she marries into the family of the richest man in Qingzhou as his wife. Her Mother-In-Law’s doubtfulness; her husband’s childhood sweetheart; her mean elder sister-in-law; her narrow-minded younger sister-in-law… Being inferior, Sang Wan withdraws without a choice. As time passed, she ended up being lonely and died tragically.

The world froze.Literally froze. The chattering students, the falling cherry blossoms outside the window, even the dust motes in the air – all suspended in perfect stillness.“Oh wonderful hero,” a melodious voice echoed through the room. “Your world faces a terrible crisis, and you have been chosen to—”“No,” he said flatly.A pause. Then a shimmer of golden light coalesced into the form of a beautiful woman in flowing robes. She blinked at him. “I... what?”“I said no. I'm not interested in whatever quest or destiny you're selling. Pick someone else.”The goddess's perfect features creased in confusion. “But... but you've been chosen! The prophecy speaks of a warrior with a fierce spirit, one who—”“Lady, I don't care about your prophecy. I've got enough problems here without adding some fantasy world's issues to the mix. Now un-freeze time and leave me alone.”“You don't understand,” she pressed. “Our world is being ravaged by the Demon King's armies! Millions will die without—”

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?