The Last Incubus with The Vice and Valor System - Chapter 147: Soon

In a world where ancient magic has been resurrected. Atlas, an orphan from Earth, finds himself transmigrated into the body of a child and possesses the rare Void Magic. Harboring such power, he’ll walk the path of becoming stronger and stand free in the sky above all existence!The tale of the Legendary Void Walker is about to begin!The cover doesn't belong to me! The title was done by TiramisuAndCoffee!

Criminal Psychologist, Su Xiao Pei, who was an leftover woman in her modern life, was informed by the God Of Marriage, Yue Lao, that her destined lover was in a car accident, his soul was sent to another world. Su Xiao Pei was ordered to bring back this strange man who was connected to her by the red string of fate. Otherwise, she will live the rest of her life in loneliness, with no one to support her.
But how does that man look? No idea.
What’s his personality like? No idea.
What does he do for a living? No idea.
Can she not go? Of course not.
Su Xiaopei, who believes in all things logical has run up against a serious wall this time.
The bottom line: This is a story about a modern female psychologist who has traveled back in time and an adorable warrior as they talk about love and solve crimes.

- Description from Novelupdates

In childhood, they were neighbors. Xie Zhen always bullied Li Yu.

Who told him to be as beautiful as a girl?

After parting for many years, they met again in the capital. With a tall stature and heroic bearing, he seemed like a completely different person.

Not only that, but his identity had also risen to that of the sixth prince.

Hearing he wanted to marry her, Xie Zhen was almost scared silly:

Σ(っ °Д °;)っ What’s his intention? Taking revenge on her?

- Description from Novelupdates

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.