When Ninjas Meet Sword Art Online

Someone who used to be a ninja learned the Seven-Blade Style from a certain Eight-Blade Style ninja. After dying while protecting a certain Two-Tails jinchuriki, they unexpectedly returned to the real world...

Starting a new life from scratch, they discovered at the age of twelve that they had somehow ended up in Sword Art Online.

Can't you just let me live a quiet, peaceful life?

If only you couldn't use ninjutsu in SAO...