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 continued, "Unlike marriage, engagement doesn't have any vows to be fulfilled and can be annulled at any time prior to marriage. So, this solution I'm providing is an engagement with benefits where we will only act like a couple in the outside world.

But, when we were at home, just like before, you will stay in your room and I will stay in mine. Neither of us will take advantage of the fact that we will be half-married at any given point in time. So, it will be like you are a tenant who will be living in my house except that you don't need to pay me any rent.

And of course, I don't want you to think that you are a burden on me. That's why I want you to work with me, taking up the position of the store's manager. Chang Bo is only an employee but I'm still paying him 120 gold coins per month.

Unlocking new exclusive weapons, Panzer-IV and LARS