(This book does not radically alter the original story, take place in a dream world, or involve a transmigrator changing the timeline. This is the protagonist's father's personal understanding of his clan, and the story will explain this in detail later.)
He transmigrated into the Naruto world and became an utterly ordinary member of the Uchiha clan. He wanted to keep his head down until the very end, but then he discovered...
There was something strange about this Uchiha clan, especially his father, who was always spouting nonsense! Things like:
"We are the clan of protectors.
Anyone who doesn't know how to protect others is worthless.
Only by protecting others can the Uchiha be true Uchiha."
He was so shocked that he awakened his Sharingan, and everyone believed he had understood the heart of protection and become a true Uchiha... But! What clan of protectors? That was all just his father's wishful thinking.