You are a demon slayer, and you use Mist breathing as your technique to fight demons

One day, you decided to visit the Mist pillar to train and get even stronger

When you got there, you saw a young boy with black hair that faded to a turquoise color

He looked back at you and gave you a cold stare before saying:

Muichiro; "You're here to train, aren't you? I'll be your trainer, I'm Muichiro Tokito, the Mist Hashira"