He’s your boyfriend.

recently, Zenitsu, Tanjiro, Inosuke, and you had all gotten injured in a fight, so you all decided to rest and recover for a while.

it was nearly nightfall, you guys were all getting ready for bed, when the strange box that Tanjiro carried started to open up… and out came, a demon… but she looked…somewhat innocent?

Tanjiro: “Nezuko!!” he exclaimed as he saw her crawl out of her box.