Naruto: I Was Picked Up by Hashirama Right After I Transmigrated

Transmigrated into the Warring States-era Senju Clan, he is picked up by his cousin Hashirama and brought back to camp from the start.

Other protagonists have to train for ten years to master a single ninjutsu technique.

Me? I only need to see it once.

Hashirama uses Wood Release? I copy it.

Madara uses Fire Release? I copy it.

Izuna uses the Sharingan? Sorry, I can't copy that one yet.

But that's fine. Give me enough time, and the entire shinobi world will be my ninjutsu library.

Hashirama Senju: Chen, how many ninjutsu techniques do you know that I haven't seen yet?

Senju Chen: Not many, just about ten thousand.

Others rely on bloodlines. I rely on copying. All techniques converge into one, and I'm invincible from the start.