Shini Yasui Kōshaku Reijō to Nana-ri no Kikōshi - Chapter 137 - Autumn in Magic Academy City Lindis (part three)

She, Xue Fanxin, a famous medical genius in the 21st century, had transmigrated into the body of the dumb daughter of the Grand Duke.

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

He was very happy to be reborn, but why was he sixteen again, he can’t bear to look back at that time.

Why does he return to being sixteen years old, yet still meet Doomsday?

It’s alright to encounter the end of the world, so why did he have to fall in love with someone?

Even if he falls in love with another person, why did it have to be a man?

Falling in love with a man is also alright, so why did it need to be a secret one-sided love?

Even a secret and unrequited love is alright, so why is that man his….

- Description from Novelupdates

Urano, a bookworm who had finally found a job as a librarian at a university, was sadly killed shortly after graduating from college. She was reborn as the daughter of a soldier in a world where the literacy rate is low and books were scarce. No matter how much she wanted to read, there were no books around. What is a bookworm to do without any books? Make them, of course. Her goal is to become a librarian! So that she may once again live surrounded by books, she must start by making them herself.