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

King Shen Niu's eyes widened in realization. He couldn't help but reach out to his forehead to wipe out his sweat beads with his sleeves and ask, "Then, what do you propose?" Shang Fu looked a bit disappointed but still looked at Mark for the solution.

Mark then said, "If you ask me, I say engage fourth prince Shang Bo to your niece, Shen Yurong. She might be a year older than him but this will also ensure a tight bond between the Shen Dynasty and the Shang Dynasty."

"Yurong'er?" King Shen only sighed in response. But the way he addressed that name stated that he was close to her. "You already know her condition. She has a weak physique and is constantly sick. Even Saint Fu couldn't cure her. We can't do that to Prince Shang Bo."

"That's because I don't waste 250,000 gold coins unnecessarily on a stranger," thought Mark as he heard those words. He then spoke in confidence, "If you give me time, I will treat her. What do you say?"

Shang Bo and the sick lady