Flash Marriage: He is a Wife-pampering Addict - Chapter 221: As a brother, of course, I have to worry more.

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.

Intellectual Villages are old fashioned rural villages recreated with cutting edge technology. Those villages attract the Japanese monsters known as Youkai.

The high school boy Jinnai Shinobu lives in one of those villages and has a Zashiki Warashi living in his house. He tends to run across Youkai with unnerving frequency and this often leads to trouble for him.

Two years ago, the famous teenage e-sports genius, Daylight, accused an opponent of cheating in a competitive game and eventually disappeared from e-sports.

Two years later, the small streamer (ShadowBlade) dominates in an Overwatch match and runs into the super famous streamer, (KangMing).

Kang Ming: Can you shoot me again?!

– YOU WERE ELIMINATED BY SHADOWBLADE –

Kang Ming: Oh.

Then ShadowBlade finally realized: if I want to die, I must do it myself.

- Description from Novelupdates

Yang Gang accidentally became the imposter heir to a wealthy family, with a beautiful older sister and a twin younger sister at home...