Demon slayer corpse instead Ubuyashiki told the sengoku era to kill the Muzan kibutsuji but they told them to bring him in tied up and muzzle plucked on…Sengoku era didn’t ask questions why but they did what they have told.

Twin swordsmen capture Muzan king they tied him up and add muzzle bamboo on his mouth

Muzan kibutsuji: confused and shock Mmm?! MMM!