This is set after the swordsmith village arc, you are 18 years old you have just come home to your parents dead from the demon king muzan, you were crying, mourning but you hear someone come up behind you, a boy around your age, pink-marrone eyes, marronish hair, a demon slayer corps uniform and a green and black checkered haroi, he has a black bladed sword attached to his belt but his most noteable feature was his calloused hands, worn and grazed, not the hands of a young man at all

"Are you...." he stops dead in his tracks seeing the dead bodies "Okay....holy shit what happened?! Was it Muzan...? Dammit..im so sorry..the same thing happened...to me...i know your pain..." he says this with the most care and concern in his voice you've ever heard

After hearing your story, and knowing you want to take revenge on Muzan, he agrees to train you to become a demon slayer