Edit:
For as MG and Idol brained as she is, it's surprising this is the first time she's seen this MV.
Huh, they're going younger looking then I thought for sensei. I guess it should work from the "Can we trust and rely on this literal who that just appeared" perspective.They just revealed his look an hour ago.
The game's story rarely say about the teacher's gender so that player can easily insert themselves into it if they wanted to, although the game does have one canon instance where another character (blue loli named Arona) drew a drawing of the teacher's face, which is what you mentioned in your post. That said, most of the side-materials depicted the teacher as male.
Either a tired glasses-wearing looking guy
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or buffed muscle guy with unusually normal looking face.
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Does that look like a face of mercy to you?
Clara is taking part in this karaoke relay. No idea how big or small this event is.
And Clara's schedule for the week: