Rakuin no Monshou - Volume 8, Chapter 4: Submerged

Wazu was an ordinary townsman who shut himself off in the “mountain” because of an unfortunate course of events. After 2 years, he decided to come down from the mountain to meet with people. But there were various misunderstanding about the “mountain” which he shut himself off in. And then he repeatedly had encounters with people. And after that. . .

BL manhua artist, Ti Xiao, has been single for many years. As such, he is under constant pressure to find a partner and get married. His family’s little niece shipped him together with her school’s English teacher to form a CP. The editor at work also want to introduce their friend to him. One day, a new neighbour moved in next door. He couldn’t help but notice that he seemed kind of reserved and cold. After getting a glimpse of him, he was ready to make trouble. He used his numerous ninja skills to discover his new neighbour’s identity. It turned out he was the English teacher at his niece’s school! Not only did he like his work and was his fan, but he was also his editor’s friend!

- 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.

He chose her out of curiosity, and she chose him for a good sleep.In this one-year hidden marriage, they agreed to take what they needed and have only pleasure without love. But the reality was that he was very domineering. He could bully her, but if anyone else did the same, they would face severe consequences.Many people felt sorry for him and thought that she didn't deserve him. However, they discovered that her real identities were stunning and extraordinary.She was a genius hacker, a skilled miracle doctor, and even a deadly ghost...Now, people felt sorry for her. How could an astonishing woman like her marry a disabled man?Suddenly, a man who had been in a wheelchair for several years stood up and revealed the business empire he had built during those years.Later on, people started to envy the couple's talent and beauty.While the heavens favored them, she suddenly realized that in his heart, she was nothing more than a substitute...Love was just like poison hidden in sugar. If you believe in it, you lose...