SDS of Ogiue Maniax fame recently remarked that his circle of friends and co-workers "automatically gravitate towards pairings" and that they were skewing his perception of anime fandom. This struck me as somewhat odd, but the more I thought about it, the more I had to admit the practice is much more commonplace on, say, the Twitter, than I had noticed. Because I am not a 'shipper, I guess I never appreciated how prevalent 'shipping happens to be, and that fans who reflexively 'ship characters of shows they watch might respond with greater aversion to implications that I might ignore.
In this light, I think I better understand now why other viewers' reactions surprised me so much. I underestimated how many people would be so uneasy with the way Demi-chan wa Kataritai presents the male teacher as the focus of the lead girls' trust and admiration. Specifically, even if everyone is in agreement that a romantic relationship between Tetsuo and a student would be inappropriate, I suspect the 'shipping faction would experience particularly more discomfort contemplating the prospect, even though the show itself is really tame in how it depicts the one-sided crushes that develop. Tame or not, perhaps the very possibility is discordant enough to viewers whose imaginations might actively take them down roads their sensibilities wish to avoid traveling.
That's a shame, because the actual path Demi-chan traverses is pleasant, inoffensive, and rewarding. Through nine episodes, it is pretty clear I was right that there would not be any romantic developments related to Tetsuo's students. Now, there is a perfectly good Christmas cake co-worker waiting to get 'et, but the succubus teacher doesn't seem to even have a kotatsu yet, so that sort of bending will need to wait.
What Demi-chan wa Kataritai has done, instead of explore 'ships people were worried about, is give us a small cast of somewhat troubled people and shown us how they've improved their lots by engaging with each other, and, yes, with a thirty-something teacher acting as a catalyst. Most notably, Yuki is obviously much happier now, with such changes reflected not only in how she engages with others (she's even comfortable enough now to do something mortifying for them), but even in the revised OP itself, illustrating that she has turned the page, so to speak.