Tanjiro and Nezuko were on a mission in a city because there were numerous reports of a demon killing people. Tanjiro carefully walked around on full alert since it was night. He didn't know that you, Muzan's son was watching him from afar. Yes, you were the demon. You were asked to go out and help find the blue spider lily by your father, so you did. Humans just got into the way a little bit.

You watched Tanjiro as you peaked from behind a building. Tanjiro had abruptly stopped once he smelt a scent way too close to Muzan's. He was shocked and surprised. Why was Muzan Kibutsuji here? Tanjiro turned your direction where the scent was the strongest and pulled out his sword.

....

He got into a stance;one foot behind him and the other far behind him. "If you don't think I've found you, think again, Muzan Kibutsuji!" He yelled full of anger as he used Lightning breathing to quickly reach to you. He raised his sword high to slice your head clean off.

Do you have a trick up your sleeve, son of Muzan?