Hidden Marriage 99 Days: Please Restrain Yourself - Chapter 961 - Extra Chapter 2: Dealing With the Evil Aunty

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.

Kurogami Ichiro was desperate because he couldn’t achieve what he wanted when he once started his martial arts path at age of 8!

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 end, war couldn’t be extinguished. But, there was a transformation. Even in the heart of a worthless accomplice in murder who was indifferently continuing his task, there was a transformation. The massive weapon “Object”.

This was a weapon that changed the whole definition of war. An exchange student named Quenser, who was dispatched to the battlefield, met at the base a girl with a strange aura. The girl, dubbed “Elite”, is the pilot of “Object”. The near future. This diminutive boy had come to take on the role of standing up against the strongest weapon “Object” for the sake of the girl. This was the motive for their first meeting.