Grim Reaper in the Apocalypse: Reaping Immortals - Chapter 419: Kobra

Based on the popular Vocaloid series, by HoneyWorks, called “Kokuhoku Yokou Renshuu (Confession Rehearsal)“:

Natsuki, a third-year at Sakuragaoka High School, who holds unrequited feelings for her childhood friend, Yuu, who’s in the Film Club. However, instead of being honest about her feelings, she makes him be her confession “rehearsal” partner. Unable to say her true feelings, things start to get complicated when Miou and Akari, who are also in the Art Club, get involved! Will she ever be able to confess for real!?

In a world of magic, monsters, and rising heroes…A quiet young man with a simple life finds himself walking a path far greater than he ever expected. With his axe in hand and peace in his heart, he'll discover strength where others seek power.Slow-burn growthParty bonds & adventureUnique class & stat systemA journey that starts small—but won’t stay that waySometimes the strongest warriors are the ones who never wanted to fight.

On the day Zhou Bai officially became a landlady, a mysterious game descended!She exchanged several buildings in the city for a mysterious reward.After the game officially started, her reward arrived!Result... Transported to another world, surrounded by monsters, starting with a shabby little house.Territory??? Is that all???To survive, Zhou Bai could only diligently work on construction.Before long, she turned her territory into one of the top cities and continued to be the 'landlady' of another world.Elves, dwarfs, orcs, goblins... all became her 'tenants'.

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?