Toaru Majutsu no Index: Genesis Testament - Volume 2, Chapter 4: The Phenomenon of Kamijou Touma — Not_Right_Hand.

Xiao Rou, a girl growing up in a poor countryside family, finds that she’s actually the daughter of a wealthy couple. Her mother had mistaken another girl for her back at the hospital. Thinking she would change from an ugly duckling to a noble swan and live happily ever after with her real family, reality strikes her in the face.

There was once an immortal cultivator fighting for the fate of human beings. Unfortunately, he failed that time; but fortunately got another chance as he was reborn once more as a human, on the earth of 5,000 years ago. With a second chance, he not only would embark on the road of saving all mankind, but also would retrieve his human nature on the new journey that would last for 5,000 years.

- Description from Novelupdates

Ace Carter Greyson, her husband of five long years forcefully divorced her on the night of their fifth wedding anniversary. Reason? Simply because she can't bear him a male heir.

Phoenix begged him to stay but his decision was firm and unbendable so she finally let him go. Her life was even more shattered after she discovered his long time affair with his secretary, and now, the mistress was pregnant. Just months after their divorce he married the impregnated secretary.

Phoenix's world suddenly turns upside down when she discovers she's four months pregnant.

[Gunfight + case-solving reasoning + decisive killing]

“I’ve been black and white, and you said I was an undercover agent???”

When Dean woke up, he opened his eyes and saw the scene where the robbers were sharing the spoils.

Because of the confusion of the original owner’s memory, Dean mistakenly thought that he was a real robber, so he chose to eat black and white, and emptied the magazine with an American-style Juhe.

Just when he was about to take the money and leave.

A blond beauty came to the door: “Dean is an intern police officer. The bank in the town was robbed. I ordered you to investigate the suspect. You don’t want to fail your internship, do you?”

It turns out that I am an undercover agent!

Dean is numb…

- Description from novelbuddy