MTL - The Whole Live Room is Knocking Me and the Female Partner’s CP - Chapter 27 027

Vainqueur Knightsbane is your average dragon: a giant, fire-breathing lizard who loves to take naps on his golden hoard, kidnap princesses for fun, and make the life of adventurers miserable. Vainqueur's only pleasure in life is to watch his treasure get bigger, one coin at a time.

So when a would-be thief turned unwilling minion tells him about "classes," "levels," and "quests," Vainqueur wonders if maybe, just maybe, he should consider a career change.

After all, why bother hunting monsters for free when you can get paid for it?

An ordinary student, a wretched peeper, a cowardly teenager with a kind heart. In a terrorist attack, he inherited the knowledge of countless elites, embarked on a path of God Jagged Tu…

He is an artist!

He is a mathematician!

He is a psychology Doctor!

He is a master of fighting!

In fact, he is a man

Taken off raw site:

A wretched, dirty young man is working during the summer when he was caught up in a mysterious explosion. After that explosion, the young man is then left with the memories and knowledge of dozens of the world’s experts.

He has changed, his heart has become cold, iron-blooded. He became a killing machine, his mind turned mechanical, calculative. Everything goes according to his plans and calculations!

In this magical, slaughterous world, a door is opened for him…

- Description from Novelupdates

This novel is also known as Long Live the Mad Wife!

Daughter of the Feng Family, born a waste. Forced to marry a fool in an attempt to expel evil influences. When the first killer from the 21st century possessed this body, the sky and the earth surged. She was indifferent and cold-hearted but she let her guard down around him alone. She thought he was a pleasant sheep but didn’t expect him to be a gray wolf in disguise!

- Description from Novelupdates