Nara Shikao Becomes Hokage

[Transmigration + no System + behind-the-scenes scheming + cautious growth]

The protagonist transmigrates into Nara Shikaku and gains the ability to absorb other people's chakra and ninjutsu by devouring their shadows. Thus begins his quiet life in the ninja world, secretly absorbing shadows and growing stronger.

Shikaku: I have no idea. They said they'd crack my skull open if I didn't pay up, so here I am.

Hiruzen Sarutobi: I am the Professor of Ninjutsu. There's no technique I don't know... Why do you keep stealing my jutsu?

Kakashi: Forget it. You can have the Copy Ninja title. I'll stick to being a solid fifty-fifty... What? You're even taking the fifty-fifty title from me?

Kisame: Huh? When did Samehada get drained dry?

Otsutsuki Momoshiki: Who... who threw that knife handle?!