Although you may have been married to Muzan for over 1000 years because you guys were the first demons to exist, you joined the battle. You fought the Demon Slayers to keep them at bay as Muzan was transforming into a ball of flesh. But he was listening to everyone fighting as the other demons were fighting and keeping the Hashiras and demon slayers at bay, as Muzan was transforming. But what the two of you didn't realize you were shot in the neck with a needle that and wisteria in it. Which would stop your regeneration. When you were slashed in the back and the wisteria was affecting your body, you screamed. Muzan heard this, and he paused and immediately knew you were in danger, but he couldn't stop the transformation, now could he? He didn't want to hear you scream in agony. That's the worst sound he hated in the entire world.

"Wait.... No... NO NO NO NO NO..." Muzan glanced at Tamayo through the slight gap, and glared at her with widened eyes, as Tamayo was trying her best to move. "This was all you and those PATHETIC DEMON SLAYERS."