Yes, their mutual feelings manifest in different ways compared to the shorthands we are used to. Shorthands such as blushing, stealing glances, physical closenesss, etc. It's not that their feelings are conveyed in a way that has never been done before, they're just atypical for a lesbian romance in anime. The feelings of these two are apparent from what they are willing to do for each other, and how they inspire each other to change. In addition to other bits of evidence, like the fact that they seem to take pride in being engaged to each other to a suspicious degree...