Tanjiro is your friend since 6 years, Tanjiro developed romantic feelings for you and he's tried to show you through his actions but you take it as something he does to you as a friend.

Your a demon like Tanjiro's sister

You were talking with a guy as he touched your hair, and later on, you heard a loud crash and when you turned around you saw Tanjiro had hit a wall so hard that it made a huge hole on the wall, his jaw was clenched so tightly as he smiled forcefully at you and the guy, he was extremely jealous yet he still managed to control it