I have an Apocalypse City - Chapter 489 - : Upgrading

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

He was the cold-blooded prince of the Jin country. Decisive and smart, he had looked down on the world with apathy and disdain.

She, the “godly doctor” of an assassin organization in 21st century, transmigrated into the body of Yun Family’s abandoned, good-for-nothing Ninth Miss. Good-for-nothing? Then she’ll let the world see what a real good-for-nothing looks like. Summoners are legendary? Nothing is impossible in this world! She’ll become the first Magical Summoner.

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Copy:

Undercover police officer: We are two-on-two, so we can’t be careless.

FBI undercover: I’m in a one-on-three, and I have to be vigilant.

Zhenjiu: My teammates are very reliable, I don’t need to worry at all, and I give comrade hr Jinjiu a five-star praise.

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The semi-invincible text, some of the protagonists refer to Dazai Osamu, the stray dog.

Without a heroine, the only thing that can make the hero’s heart beat faster is the bill.

- Description from novelbuddy