now what?
Uchiha Itachi Nakamura Shisui was six when he got his quirk.
All his classmates had their quirk at 4, and his parents started to worry that he was quirkless ('useless' his father mentioned). Lucky him, he was just a late bloomer, but unlucky him, his quirk is useless in his father's eyes ('What do you mean his quirk's knowing his past life? It's useless and he isn't even my child anymore now.')
When he received his quirk, he found out at his past life he was a ninja, a murderer (red liquid dripping over their dead body and his past self not even flinching). There were no quirks, they used chakra, there were no heroes, there were ninjas. He heard a scream from the compound, and then he woke up.
His past self was cool (except the fact he slaughtered a whole clan but let's ignore that) and had a sad past (he didn't know if it's a coincidence or not, but his name is the same as his past life's best friend, not cool life wtf?)
He was cool, calm, and collected like he is (I mean, technically they are literally the same person) and absolutely insane (he couldn't imagine living in a world killing is normal, the chaos). Now, he isn't a bad person but he got to admit, that shit real cool.
His past self was a prodigy, a smart and bright person (like he is) and PEOPLE THREW FIREBALLS WHAT. Apparently, his past self sacrificed himself to save his brother, Sasuke who for most of his teen life tried to kill him (now, if this wasn't a plot of a story he doesn't know what is.). He was also part of a criminal group (The Akatsuki, dawn huh) and was partnered with a half-shark half-human (he was about to call it weird but then he reminded himself he lived in a world where people have extra body parts)
Oh, right did I forget to mention he got a fuck ton of mental disorders?