Snowstar

Mark is a genius military weapon designer who was kidnapped by a mafia gang after refusing to work for them.
They forced him to design unique weapons for five years, until one day he successfully escaped only to get shot by his trusted comrades.
*Ding! You awakened a weapon system.
When he opened his eyes, he was in a different body and in a different world.
"You want to kill a wild boar without being detected? Forget about bow and arrow. Here, I present you this sniper rifle."
"You want to kill a horde of goblins from the sky? Forget about those flying carpets and brooms. Here, I present you the fighter jet." 
"You want to kill a dragon? Forget about taking the help of the S-class adventure team. Here, I present you a nuclear bomb."
Join Mark Spencer/ Lu Zhen as he brings the whole world to its knees with the help of his weapon system.
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Note: Author isn't born in an English-speaking nation and has no editor either. So, please be understanding if there are any grammatical errors.
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Author's current works: War Online, My Soul card is a Reaper
Author's other notable works:  The Last Slytherin, The Sharingan Hyuga
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You can also support the Author through Patreon

https://www.patreon.com/snowstar

Weapon seller in the world of magic

"Song Yue, this is Black Knight, a peak stage 6-circle realm expert from the Western Moon kingdom. I have hired him for your protection in my absence." Mark introduced the disguised Song Yun to Song Yue as a guard, surprising her a little bit.

Song Yue was taken aback, not expecting that Mark would hire such a strong expert. She doesn't know how strong this man in a knight's armor is, but as the former heiress of Song Clan, she does know that his security services won't be cheap.

She asked, "How much it will cost for his security?"

Mark actually didn't prepare for that question. He thought Song Yue will ask him whether there is a need for an outsider when there was Allen and Alina.

As he was thinking of a price, along the lines of somewhere between 300-400 gold coins per month, Song Yun raised his hand and gave the reply through writing. It didn't take long for the words to appear in mid-air.

Mark meets Zheng (part-1)