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

Mark's explanation of each model that was withdrawn from the display in the store earlier lasted for more than an hour.

After a while, the three of them came downstairs and Chang Bo helped Mark with the packaging of the weapons while the latter purposely gave the task of calculating to Song Yue so that she found herself doing her job.

Song Yue was an educated woman who was taught by the Royal Tutor. While she might not be as intelligent as Shen Ling, at the very least, she knew how to make calculations without making mistakes.

As Mark started to speak of the order, she opened her notebook where she recorded the prices of the weapons and explosives available in the store.

In the end, the bill totaled 10596 gold coins and Lan Jing paid the amount with medium-quality ether crystals of 10-carat sized, each one equivalent to 100 gold coins worth.

Mark was happy to receive 106 of them as he was in need of them more than the money anyway.

Shang Jiao confronts her mother