MTL - The Reborn Scholar Wants To Counterattack - Chapter 2 The most annoying person in this life

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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A wicked mother one day brought home a girl. The child was the hidden legitimate daughter of the duke, the heroine of [The Duke’s House Has Three Sons and One Daughter] Loretta. I was Melody, the villainous girl who tormented her and was condemned along with my mother. Not wanting to die like that, I decided to start treating her well now. I personally fed Loretta, put her to bed, and played with her. And then her reaction was…? “I want Melody to marry me!” Caught off guard by her endless affection, I too ended up entering the duke’s family, “I’ll stick right by Miss Melody’s side.” And there, it seems I’ve met a young lord who’s an even bigger ‘Melody fool’? All I did was be kind to survive, but why am I being loved…?!

Transmigrated to become a disciple of the demon sect, relying on the technique modifier to become a giant of the demon path.

[Detected the technique “Blood Nerve”, relying on devouring blood to cultivate]

[Side effect: easily affected by the spirit contained in the blood, becoming bloodthirsty, murderous, insane, and even brain dead]

[Please wait, system modification is in progress…]

[Ding! Modification completed and side effects canceled]

The world is terrorized by the powerful Black Witch who has been sealed in the moon. Every ten years, the night of Hexennacht arrives and a chosen witch must battle the Black Witch in hopes of finally defeating her.

As the current decade’s Hexennacht approaches, a mysterious girl named Kagami Kagami arrives and meets Horinouchi Mitsuru, the daughter of the previous Hexennacht representative.

It takes place between Kyoukai Senjou no Horizon and the City Series, two other series by the author.