I got to the demon+slimes boss with just one character, I think I missed a trigger somewhere. I also didn't fight the succubus pair the first go so I think I somehow skipped that trigger too. It seems that holding the run button (Shift) or progressing through dialogue too fast seems to cause some events to behave strangely?
odd, since the succubus pair is an autorun event, unless you meant that you went to the boss without first rescuing sylphie after losing. but there should be an automatic loss event if you try to go to the boss room without her.
At the time, the game acted like I had her with me in dialogue before the boss fight and then after I lost, the game still acted like she was there during the bad end. So I dunno.
there really is an invisible barrier that triggers a scene when trying to get to the boss room alone... what order of events occured to let you get there? cause you normally lose the key to the warehouse so you need sylphy to open it
I never met her in my first run. I went in, retrieved the warehouse key, no succubus pair fight happened (IIRC I moved through the lower route between crates I think), I used the key, I navigated the warehouse (also pushed the boxes into place while there) and got to the boss, who I got to and then saw the bad end.