Now, that I can't tell.
Oh? Though the door isn't locked.
Huh, dunno why I thought it was locked. Oh well, guess there's no point in bothering to use the Dumpty Key on it, might not even be a hole to stick it in.
The way you phrased it about getting an unexpected result makes me believe there is a key piece of information about the situation we haven't been given any glimpse of yet (hence why the result will be "definitely" un-guessable) that we will run into if we try to 'coax' the domain into doing something.
My first instinct was something along the lines of what
@quantum lurker suggested, which I think
@Nero200 first brought up earlier, about the place being an amalgam of multiple Scavengers' dungeons. Meaning multiple "deepest" rooms and possibly conflicting psyches to try and appeal to. My next thought was the opposite - no boss room at all. If we got to the end the normal way, there might just be a black hole there or a gap leading to some other part of the wider cognitive world, because of how much the place has been falling apart.
I think I'd rather find this stuff out singing from the safety of the corridor outside the actual dungeon, than after wasting energy venturing in or tearing a hole, only to find there's just a pit at the end instead of a room. Or another set of doors to more sub-dungeons or something.
I did notice you suspiciously didn't guarantee Yui would be rescued even if we retreated and Naoto called in her whole crew of veteran Persona users, hinting that outcome might never have been in the cards from the start. This makes me suspect Yui may not even actually be in there either, just her Shadow. The actual one might have been kidnapped physically with the rest of the Scavengers and this whole thing is the result of a failed escape attempt or some Hail Mary cry for help sent using her psionics.
So I'm up for checking the wildcard result. Especially since being conducted from outside the Abandoned Laboratory should likely limit any potential downside to the party.
[X] Plan - Meikyuu Butterfly: Convince the 'shadow castle' to shift the room with the physical Yui right in front of the door. Joint action between Utau and Amu.
-[X] Main Actor - Utau: The same skill, once used for the nefarious deed of blackening the hearts of children, perhaps now may serve a more noble purpose. Empowered by the Dumpty Key, hand-in-hand with Amu, reach out and connect to the 'mind' within the fog. Like a butterfly wandering a labyrinth, you feel your way towards the darkened depths of Yui's suffering and beckon to it, singing out your earnest desire to step across and share in her pain:
"Open your shiny eyes in the silent night..."
--[X] Use Lightsmithing to seek out the mind behind the fog and guide your beckoning.
-[X] Sub Actor - Amu: Utau has not met Yui or felt the 'mind' of the 'shadow castle'. You have. Share your experiences with Utau to describe how you did it and what it felt like, in order to help her do the same. When Utau beckons, add your own emotional voice to the choir of Utau's melody, sending out the whispers of the respite you promise to bring:
"I continue writing out the pages of my story, even while I'm blinded by the fog of destiny, I'll be breaking through the clouded skies toward tomorrow's distant light, high up in flight..."
--[X] Provide free pre-concert refreshments for everyone with Su's Happy Fun Cooking Time.
-[X] Send Ami and Midori back to rendezvous with Hikaru and update Tsumugu. Tell them to try and make sure Hikaru doesn't panic and do anything rash.
