Valerian Empire - Chapter 96

Banaza was summoned to The Magical Kingdom of Kryrode as a Hero Candidate, however, due to having only the abilities of a regular citizen, he was treated as a disqualified Hero. He, who was originally supposed to be returned to his original world, became unable to return, due to the Magical Kingdom’s mistake, and, inevitably, had to live in this world. However, the moment he became Lv2, Banaza acquired every attainable skill and magical ability, and he became a Super-Cheat with Stats that transcend normal limits! Even so, Banaza , who does things at his own pace with an easygoing smile, takes Lys of the Demon race as his wife, and fully enjoys his newlywed life. He then changes his name to Furio and leads an even more laid-back life! However, chaos is in store for the Furio household; on top of a strange pet and four, freeloading Female-Knights, even a Devil and Former Demon King join in. Despite his circumstances, even with his life becoming increasingly chaotic, Banaza continues to enjoy his laid-back lifestyle. Please enjoy the story of the everyday life of the Furio family, which, with the birth of the twins, gets ever increasingly laid-back. Included is also the story of the man who became a Hero in Banaza’s place!

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.

She is a waste daughter from the Su family that couldn’t cultivate. On the day before her wedding, the Third Prince breaks off their engagement in the street. Her own sister replaces her in the marriage to the Third Prince. She became the center of gossiping in the city. In her resentment, she hits herself on the Su Family’s gate, only to become the object of other people’s ghost marriage.

The eternal struggle between good and evil, Qin Shuang steps onto the path of cultivating, meeting various heroic individuals on her way to immortality, experiencing various events on her journey.

- Description from Novelupdates