Shinigami in the Ninja World - Chapter 215: Ōken and Hueco Mundo

Sincere is transmigrated person, who gain a magical tiger eye in his left eye. with this eye he decided to change his ending and became the richest person

A decade ago, the first dungeon gates appeared, but some vanished before they were ever conquered. The MC, a low-rank hunter, awakens the Lost Gate System, granting him access to these forgotten dungeons where legendary monsters and artifacts are trapped. Each completed lost gate grants him absurd power, but also reveals terrifying truths—these dungeons are prisons for ancient beings who want revenge.

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.

“Master. Why do you never visit?”“Shh... Just take this needle and don't make a sound.”The act was getting old, Teriyaki had only spent a month in Orochimaru's Lair and he was already close to ending it all.Just a month ago he had been a normal human, flipping halfway through the naruto manga when he fell asleep on Chapter 45... The place where that darned Snake first appeared.One more Teriyaki is an NPC or worthless comment and I will find you.TW: torture simulator kinda at some points