just some loose thoughts but... this is one of the few times we get any information about the current Ohtori staff. Utena is clearly talking about the guidance counsellor/teacher (we do see her teaching a class in episode 16) who continually harasses Utena about her prince's uniform.
at first when I saw this scene I thought it was "Alum" as in short for "alumnus" but that's actually not the case. it's ミョウバン which means "alum" in the chemistry sense; a hydrated salt of aluminium (often potash alum). now why on earth would everyone nickname a teacher (who has nothing to do with chemistry) something like that. are they calling her astringent?
it has a lot of uses historically in manufacturing of things like paper but it was also used to adulterate bread — to make bread made with low-quality flour look whiter than it actually was. in english it was called "baker's stuff" when used for this purpose. it struck me as interesting considering that Utena also talks about bread rolls in this episode and leaving them out overnight?
of course, it's also used in alchemy, which given the other alchemcial references in the show is probably more relevant. 🝅
alchemical symbol for alum in Nicaise Le Febvre, A compleat body of chymistry, London, 1670
obviously the scene also gives the implication that the teacher has been there a really long time and fits in with the time stuff in the show also.
