He traveled through time to become the Hokage of the same class as the Fourth Hokage, brought with him the Bankai Lottery System, and accidentally became the biological father of Naruto and Sasuke?

Original creation plus fan fiction presents a different Naruto world.

Madara, "Obito, you must pay attention to that man. He may be your biggest obstacle in the future!"

Black Zetsu, "What?! You want to join forces with me to rescue my mother???"

Obito, "Why are there so many vampires in Akatsuki?!"

The Otsutsuki clan, "This is a race that is even more powerful than the Otsutsuki!"

Yuuki traveled to the beginning of World War II in the Naruto world and became a spy trained by the Root.

During a mission, he awakened his vampire abilities.

From then on, Yuuki used his vampire abilities to develop blood escape, enslaved ninjas from various ninja villages, and gradually became the strongest!