Nah, on some level I do believe there is some love beneath all this. Despite all the rampant degeneracy, Yuika was shaking when she tried kissing Keiki. Sayuki herself only became "outgoing" when she was sure Keiki would accept her. On some level, I could see the girls using their "fetish" as a mask to hide the love they feel for him since it would take a lot of courage to confess while having these "personality problems", hence the (almost forgotten) confession letter and pantie.