A Question about Tsukiakari no Rasberry

So, (I don't know any character names) I'm watching the opening movie for the game on youtube, and it appears that the futa teacher is in a relationship with one of her students. From what it seesm in the movie theatre, the student is the strong one and the teacher is the submissive party. If that's the case, then why does the student 'receive' (in the dominance/submission sense)in alot of the cutscenes? Just wondering, since I can't find anything out about the plot of the game.