She was born into a wealthy family - Chapter 597

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.

"When will people understand.... I'm only half insane?"

Crossing to One Piece world, he became Roger’s younger brother.

Unexpectedly, Gol-D-Roger who was in his fifties had a teenage brother. But he was so weak.

Fortunately, at the age of sixteen, he actually found himself with a possession soul system.

He had attached to the master IP man, also to the White Phoenix and to Ge Nie with his strong ability of the Hundred Step Flying Sword.

If you think that he can only Purchase these? Then you’re wrong!

Pain, Itachi, Ichigo Kurosaki, as long as there is money, any soul can be Purchased.

- Description from Novelupdates

The light is here because the darkness exists. Just like that, the human realm exists because the demon realm is here. And in the great palace of the Blade Empire, a crown touches the peak of its glory before it falls from its grace. Lush Von Blade was the royal crown prince of one of the greatest empires on the southern continent. He is loyal but betrayed.On the other hand, where even the Gods fear to set a foot on, a demon lord abides. His grace and cruelty have been unseen for centuries. He is the supremacy in the three realms. While Lush is the light, he is the darkness. Each exists because the other is here.