Redemption

Massive Manga Spoilers!!

He regrets it. He regrets everything. He wishes that he could turn back time and change the damage he did and the lives he took. However, life isn't that easy, so he must keep on living.
400 years later, Tanjiro finds himself in a modernized world, demons long forgotten. People around him developed powers, which they call quirks, that allow them to do things that back in his time, was only possible for demons or demon slayers. Unfortunately, with these so called quirks, came people that used their powers for their own selfish desires. This led to the emergence of heroes and villains.
After watching this from the sidelines, Tanjiro decided that now was the best time to take action and finally show himself.

He wanted to change, he wanted to start over, he wanted redemption.