Maybe i'm not thinking deep enough, but it also could be the deeper meaning was just a distraction to a darker plot. His friend says he and the teacher always talk together and she does seem to do a little extra for Fukano, it is possible that she was drugging him to have sex and dementia was a side effect. Before possibly molesting him she says, "forget everything to today as well", makes it seems like she knows something about his ailment. As a result of his resistance she probably stopped her advances and never said anything to reduce the risk of her being discovered.
She knew all along he didn't steal her panties, but used it as an excuse to keep visiting his house. Which is why she said she knew and also to eat her to view her memories just to be certain of that and her love.
Makima is a piece of shit, but me too so... Denji X Makima <3