One Piece: Supreme Check-In System - Chapter 78: Demon King vs. God Knight Shamrock

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.

Traveling through different worlds – this is unscientific!

Get cheats – it’s science!

…

This is a simple story. An ordinary person lives in a different world, farming and raising flowers, studying unscientific science in his free time.

until the end.

- Description from novelbuddy

Become famous as early as possible, make money as early as possible, and enjoy the joy of life in America with both fame and fortune.

America, Hollywood, business war, entertainment, celebrities and movies.

- Description from novelbuddy

“Blonde again this time.” It’s already the third time being possessed. The third time with blonde hair. At this point, I can’t help but doubt the taste of the deity I serve, Pebula. Upon waking up, the detailed personal information of the third body, Siora, is as follows: [Siora Velvet. 20 years old. Parents died in a fire. Currently under the protection of Count Bonetti. Remaining assets: 0g. Scheduled to be evicted in 3 days] It’s clearly a worse situation than the previous two possessions! *** As the only priestess, cleric, saint, and pope of the ancient deity Pebula, one day she received a book. The book titled described that the world would soon be destroyed by the villain ‘Cruello White Desert.’ “Ancient deity Pebula, please perform a miracle.” As soon as she finished reading the book, Pebula, who had given the revelation to ‘Reform the villain!’ immediately threw her into the body of the villain’s childhood fiancée. First attempt: Died after being poisoned instead of the villain, thus failing. Second attempt: Possessed the body of the villain’s maid but also failed, as she was too focused on doing nothing but dying. Finally, the third attempt. Waking up in the body of Siora, who had no connection with the villain, she strives to make a connection with Cruello. However, there is only one year left before Cruello destroys the world… Moreover, after two failed attempts, the once innocent child has already grown into a wicked villain! Like Cinderella returning home at midnight, Siora wants to save Cruello and escape her duties. Will she be able to fulfill her role and break free from her fate? #Overpowered #MultiplePossessions #PoliticalMarriage #Revenge #ComingOfAge #Redemption #SaintOfAncientDeity #ReformTheVillain