This is for those who are hurt over no actual door during gameplay
There is already a domain. Everything goes creepy Black and white, candles start appearing on the ground we walk, we start hearing spirits whispering and the Mongolian throat sound is there and we hear bells and the door closing at the very end
Why we don't see it ? From kuro's perspective people will love it at first then start complaining about the door getting in the way of their combat.
If it's physical then... Well obviously that'll cause issues
If it's not physical it's still a visual wall that if ur enemy ends up on the other side could be quite irritating mid combat
So my head canon is that he purposely makes the door invisible to himself upon calling it so it doesn't get in his way... But it's still there ofc, since we hear it close