Re-Birth Of A Genius. Creator/Destroyer - Chapter 37: Sam the Tailor II

In this fantasy world, music and aether rules all. However, there is constant threat of demons and natural catastrophes. The most powerful men are musicians who use music, alchemy, and spells to safeguard their homes. A young man who just wants to find his father and know why his family was exiled, starts his journey of becoming musician – a journey that leads him to the crown of justice and glory.We are born of aether, grow under aether and die as aether. Awe of Aether! – Holy Code.

Takahiro Nao, a 25-year-old burdened by crushing debt and driven solely by his love for his struggling family, meets a tragic end—until a mysterious Goddess of Benevolence offers him a second chance: reincarnated in another world, and his efforts there will provide for his family back on Earth. Awakening in the body of Naoki von Blackmore, a disgraced “Failed Hero,” Nao is thrust into a realm of sword and magic, monsters, and war, tasked with the impossible mission of defeating the Demon King. With newfound powers, a shadowy past, and the weight of two worlds on his shoulders, he must battle not only relentless enemies but fate itself. Blending emotional depth, thrilling action, moments of humor, and a spark of romance, this gripping isekai adventure asks: how far would you go—and what would you sacrifice—for the people you love?

It begins on the mountain.

With the glint of a knife, a flash of steel in the hands of a sworn brother. A betrayal.

Stabbed and pushed down the mountain, Zi Chen lied within the red-stained snow, left to die.

This is where it begins; he is given life by lightning,
baptized by thunder.

Those who had once betrayed him should all suffer in his cruel revenge.

- 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