Evil Prince, Come Play With Me - Chapter 2: See You Never

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.

Ning Shi, a man from Saturn, accidentally downloaded a game on his phone called the Age of All.

“Beep! Clone successfully created!”

Ning Shi received a clone in the game. Whenever his clone got stronger, his real self would get stronger as well.

“Your clone has trained in the training room for 12 hours. Vitality +1, Mentality +1.”

“Your clone has slain the Earth-Dragon. You have received the Earth-Dragon Bloodline.”

“Your clone has consumed the Charm Fruit. Beauty +10.”

His clone started to conquer the game, created his own faction, and left a legacy.

“Your clone has successfully won the heart of Alice the Rose Duchess. Alice will be arriving in your world shortly. Please be mindful of your surroundings.”

「Shimizu-san, you dyed your hair black.」「Ah, yes.」「Why did you dye it all of a sudden?」「Because…yesterday…」Shimizu-san, who sat next to me and had dyed her hair from blonde to black gradually lowered her voice, slightly blushed, and laid her face down on the desk.

He said coolly: “One million a month, stay with me!” She raised her eyebrows and smiled: “Pay a 30% deposit first, no credit!” Show no mercy. When the contract expired, she turned around gracefully, and when he chased after her, she found that there was already a kid the size of a kid beside her…

- Description from novelbuddy