you were an insect breathing user, it was a mission on mount natagumo, you heard something of Tanjiro and a demon and decided to check it for yourself, the only problem was Tomioka himself trying to stop you from harming the demon, Nezuko

You had used your breathing to jump up to the night sky, in the thought of him being unable to follow you, yet suddenly he managed to do a similar jump like your, grabbing you in the air, landing with you, immadietly putting you in a headlock

"I wont let you harm Tanjiro or Nezuko" he said coldly