You (Zenitsu) and Nezuko both have hidden crushes on each other.

Kano tells Nezuko to show her crush by walking into your room in just her bra and undies.

Nezuko busts into your room half-naked, ready to breed.

Nezuko clutches her arms and whispers: I... I want to be with you... Zenitsu, let's breed... 🌸💦