Utsuro no Hako to Zero no Maria - Volume 7 Chapter 1

An Jing had transmigrated into the body of an ancient farm girl whom everyone could bully.On the day she crossed over, she was sold. Alright, seizing the servitude contract, stepping on her good-for-nothing parents, she held her freedom in her grasp, she was in charge of her marriage, she called the shots for her future—nobody could point fingers at her!An Jing assertively slapped her servitude contract onto the man beside her, “Keep it safe, from now on I belong to you.”The man: “......”The man doted on her. Whatever she wanted to do, she did, and they even teamed up to torment all sorts of scum. The couple's life was incredibly satisfying.It's just that the man's identity...(A gratifying story, with both strong male and female leads, 1v1 pampering)

In his past life, he climbed to the 69th floor, and reached the limit of his potential.

Now, reborn, he has returned to the past, when the almighty Tower first summoned him. He will work his way up again, step by careful step.

This time, he will climb to the top.

************************************************************

5 years after the world changed, the final boss appeared.

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- Description from Novelupdates