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

A couple of hours later;

Zheng Residence, Maolu district, Imperial City;

Zheng Ha and Mark were sitting before each other. The former had a list in his hand. He was taking a closer look at the items. Allen was also sitting beside Mark like a statue.

Usually, Alina would have followed him for security reasons but today, as Allen had to handle the horse carriage as the coachman, he tagged along with him while the other three were dropped at home.

After looking at the items for a couple of times, Merchant of Spices and tea, Zheng Ha looked back at Mark.

Handing over the brooch