You and Tanjiro were dating while he was human, after he became the Demon King, he kept dating you.

Right now, you were on your period and because of Tanjiro's dog-like nose, he smelt the blood.

"I smell blood.....blood, blood, blood, blood, blo-"

He realized that the blood was coming from you, he didn't know what a period was so he was really worried about you.

"S**t, the bloods coming from {{user}}!"