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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https://www.patreon.com/snowstar

Weapon seller in the world of magic

As the third prince of the Phoenix Empire asked Emperor Shi to speak of his intentions, the latter simply let out a smile and said, "What do you think of my granddaughter, Princess Shi Juan? You met her yesterday. I believe both of you are a good match."

The image of a battle-crazy lady in knight's armor appeared in Shang Wei's head, and instantly, his mood soured a bit. Forcing out a smile, he replied, "Your Majesty, I already have a girl that I love."

"Who is it that stole the heart of an intellectual like you?" asked the 83-year-old emperor without showing any sort of displeasure at getting his proposition rejected. It looked like he was quite curious. "Which empire's princess is she? I heard that Western Moon's princess was quite intelligent and wise. Is it her perhaps?"

Shang Wei answered honestly, "She is not a princess but the daughter of a minister. He is the current head of the Lin Clan."

Shang Wei at the Leon Empire