A Step into the Past - Volume 20 Chapter 2

The world ended, seven days of earthquakes, volcanic eruption and then came the meteor storm, bringing something worse—mutation.Now, survivors are group into Shifters, mutated humans and normals.Ava Zhang was supposed to be a Normal. Useless. Disposable.Thrown into a military-controlled bunker, she is sorted into Level Three—the bottom rank, where the weak are left to rot. Starving, overworked, and surrounded by desperate scavengers, she realizes that in this world, strength decides survival.But Ava isn’t as powerless her hidden System activates. The Blueprint System—an ability that lets her design and invent anything, from weapons to high-tech defenses.

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

A little ruffian who fought recklessly without any morals and bottomline accidentally time-traveled to parallel space and became a Key Case Investigation Team agent. The huge change in identity had him creating chaos in the police station. However, a strange miracle system helped him repeatedly solve mysterious cases, turning him into an impudent ruffian detective!