Hmmm, I'd like to see more of the café owner, perhaps she and Sensei might get together … Something along the lines of "Amane seems upset, maybe I should speak to her teacher" - okay long shot, and perhaps not the most logical train of thought, but I can fantasise.
Sensei definitely seems, to me, to be getting shown by the author too much to be left out of future plot development (though could be way off the mark with that).