1) Managerial Offices
-If Jadeite (?) is in the building, he's probably here. If we want to get him alone with no immediate allies to hand, this would be it. If it's not him, there's a good chance that
someone in charge is. Either a brainwashing victim we can
Moon Tiara Stardust to get some help figuring out what's happened, or a youma involved with the plot.
2) Studio Floor
-Also a reasonably good chance of finding someone important to the plot. I don't know if the Caravan's normal business is proceeding as usual.
3) Recording
-Some chance of finding, eh dunno, Miss Takahashi. Likely to be technicians here who we can un-brainwash for intelligence on the situation.
4) Dark Room
-Theoretically for developing photographs. Remember, it's the '90s. Digital camera technology is in its infancy;
film cameras are the norm. It's possible that there's some punning going on and that the youma have taken this area over as a barracks or something, but this is a legitimate area you'd expect to find here.
5) Talent Offices
-See (3). Hard to predict exactly who we'd find here. If Mikan (who goes to our school) had any single place in the building that was
hers, it'd be here. And Mikan was canonically replaced by the youma who ambushed her in the shower, then imprisoned and impersonated her. Here, "Mikan" is the one ringing the chimes, which strongly suggests that the same thing is going on here.
6) Break Room and Staff Kitchen
-Hard to predict who we'd find here, again. With the staff clearly brainwashed there might not be anyone here. On the other hand, this is one of the most conveniently repurposable spaces in the building if the youma are setting up a barracks or need a weird runic array to sustain the brainwashing or something.
7) Front Office and Lobby
-This is a great place to control entry and exit to the building... which we have no particular need to do.