Valhalla Saga - Chapter 229 - Episode 65/Chapter 3: The ten realms (3)

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.

How could a poor graduate student without any background or connections become successful? With a coaching system? An upgrade? This is not a computer game, but real life we’re talking about!

Roan crossed over and became an FBI agent.

Several years later, when interviewing the world-renowned detective Roan Greenwood, the reporter asked:

“Excuse me, what made you persevere on the road of solving the case?”

Roan tilted his head and glanced at the sports car beside him, the villa behind him, and the beauties in the villa, and smiled slightly:

“Of course it’s the bonus after solving the case.”

“???”

- Description from novelbuddy

The romantic comedy light novel series centers on the gaming lives of various high school students who play video games, including: Keita Amano, a lonely young man who loves video games; Karen Tendō, the beautiful president of the video game club; Chiaki Hoshinomori, who constantly fights with Keita; and Tasuku Uehara, who puts on a facade of being satisfied with his life in the real world, but he in truth loves video games.