After Becoming a Solo Player, My Unlimited Skills Made Me Invincible - Chapter 191 - : Changes in the Tianyuan Battlefield, Earth’s Technology Is Still Here?

Shuu is a member of the literary club that can’t write. One day, he gets a mysterious message on his phone from a girl called Eina, and from that impulsive contact, they begin to exchange messages. They talk of things like their shared interest in novels and grow close. However, when they try and meet, they discover a shocking truth. Eina lives… not in the present, but five years in the past! How will their love develop, parted by five years of nights…!?

In the Canglan Continent, there existed a rule: only those who managed to awaken a Martial Spirit were able to pursue the path of cultivation, and a Martial Spirit’s rank was determined when it was awakened. Born in Linshui City, Qin Nan was a peerless genius who possessed great talents and was highly anticipated to become a great cultivator in the future. However, things changed when he ended up awakening the lowest-grade Martial Spirit, resulting in him being considered trash.

Dressed as [fantasy world] [patriarch], portray the fantasy world as realistic as possible from the perspective of the family, grow spiritual fields, raise spiritual fish, develop various family industries in an all-round way, support salted fish elders to become ancestors to serve as umbrellas, and inspire juniors to bravely venture The Holy Land Academy has come to the fore.

It is not a fantasy of passionate combat, but is based on the promotion of various family industries, capital, facilities, domestic servants, family generals, clansmen, guest officials, in-laws and other elements. Trying to see the “old-fashioned” fantasy world from a fresh perspective.

- Description from novelbuddy

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.