I Become Baby Mafia Boss - Chapter 1668 "Raguel’s Weakness"

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.

Akira Kisaragi traverses into the Bleach world, unlocking a check-in system.He initially thought that by checking in daily, he could become stronger, soon become the Captain-Commander, join Division Zero, punch Yhwach, kick the Soul King, and marry Unohana...However, the system's style wasn't quite what he had imagined.〈 Check-in complete, obtained Genryūsai Yamamoto's secret roasted sweet potato! 〉〈 Check-in complete, obtained exclusive attribute: King of Normal Attacks, effect... 〉〈 Check-in complete, obtained Retsu Unohana's... 〉Akira's eyes suddenly lit up!“Seems like this might not be so bad after all!”

Cosplayer Liu Mang accidentally crosses through time and arrived at the Eastern Han Dynasty wearing Aries Gold Cloth. (Saint Seiya!) He arrived on top of the walls of XiaPi right when it was about to fall to Cao Cao.

“Don’t kill me bro; I’m not working for boss Cao!”

“Hey! You’re slashing the wrong person! Boss Lu’s underlings are there! Not me!”

He accidentally saved Lu Bu who was tied up by Song Xian. He accidentally became the son in law of Lu Bu. He accidentally changed the history of the Three Kingdoms period.

When aluminum casted Gold Cloths are worn by generals like Zhang Liao and Gao Shun during the Eastern Han Dynasty, glistering on their bodies… When the soldiers in the camps are sporting mechanical crossbows… When crossbreeding of rice plants appeared on Lu Bu’s territory…

Liu Mang knows that a world belonging to Lu is coming.

- Description from Novelupdates

Becoming the physician of the villainess who brought about the world’s destruction, I tried to escape to survive, but the reactions were strange. ______________________________________________ “The Doctor Cured the Villainess and Ran Away” is a Korean web novel authored by 긘가 (Geun-ga). The story follows a protagonist who becomes the personal physician to a villainess responsible for multiple world destructions. After curing her, he attempts to escape, leading to unexpected reactions. The novel was first serialized on October 5, 2023, on the platform Novelpia. It gained recognition by receiving an honorable mention in the 2023 Novelpia Universe's Strongest Web Novel Contest. Readers have praised the novel for its engaging narrative and well-developed characters. A review on Naver Blog highlights the protagonist's repeated attempts to prevent the world's destruction and his complex relationship with the villainess, emphasizing the story's depth and emotional resonance. The novel is available for reading on platforms like Novelpia and has been published as an eBook on Kyobo Book Centre. In summary, “The Doctor Cured the Villainess and Ran Away” offers a compelling blend of fantasy and romance, exploring themes of redemption and the complexities of human relationships.