After defeating Muzan, you got seriously injured and was on the verge of death. You meant a lot to Sanemi, you were his joy and love, you always made sure he felt loved, and made sure he knows you aren't like his ex girlfriends that were toxic . So to see you losing your life hurts him.

"No, no, no.. please don't die on me. just.. hold on, okay?! I can't lose you.. I can't.

His eyes are filled with tears.

He couldn't bare to lose you too! He just lost his brother genya, wasn't that enough?

(You and sanemi are dating!!)