Raidorl Seiken Senki - Chapter 13: Determination and Ambition.

Due to a mistake on his student’s part, a super Martial Artist had received a wrong class in an online game and had become a mage. He who was used to curbing violence with violence and using strength to subdue strength could only make the best out of his mistake. Taking on a new lease in life, he became a violent close combat mage. When strength and magic came perfectly together, a new gaming path had been opened by him!

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“Fireball spell? Lightning Chain? Frosted Ice Mirror… etc.”

“Wait, I came here to practice Kung Fu! What has magic got to do with me?”

“I am a mage?”

“Oh, that’s right. I am a Mage!”

“However… do you really firmly believe that I am a mage?”

“Alright then, look at my knives! Look at my sword! Look at my fist! Look at my concealed weapons!”

“What? You’re now saying that I’m not a mage?”

“If you don’t believe me, I will prove it to you: If you believe me, I will show you a performance: No one can get in the way of a mage who knows Kung Fu!”

- Description from Novelupdates

Doomsday Online has descended, reducing the entire Earth to a ruined playground. It is occupied by countless terrifying monsters.

Amid a world war, with his awakening to powerful special abilities (Soul Armor Abilities), Kamiya Yuusuke, conscripted into the military at the age of 10 due to this newfound power, continued to achieve numerous victories on the challenging battlefield. As a result, at the age of 15, he held the position of Brigadier General.Despite traversing battlefields worldwide, he finally managed to return to Japan. The joy of returning home was short-lived, as news of an underage boy in the military started to leak to the public. In response, the military high command ordered Yuusuke to attend a military school called the Special Operations Soul Armor Academy and undergo a revision of his military records.Yuusuke, secretly pleased at the prospect of reclaiming his youth, faced numerous troubles, whether due to the nature of the unique school or perhaps because he had been in constant battle since childhood. What will happen to his relationships with strong-willed girls such as his half-silver-haired childhood friend, the older sister officer who is his work partner, and the tsundere honor student of the same age?

In the era of universal mechas, people can go to the endless abyss, collect materials, strengthen and forge their own mechas, and master the power of destroying the world.

Jiang Chen traveled through time and awakened his talent [Immortal Unarmed]. Once the mecha is broken, he can permanently absorb its power and receive multiple bonuses.

…

At the bottom of the abyss, when the Old Demon God finally broke the Titan mecha with great effort, a hand stretched out from the fragments and held down its head.

“Congratulations, you have unlocked my limiter.”

- Description from novelbuddy