So in terms of interesting things I found since my last comment, I found out that if you have unlocked sex scene with Selma, and initialte with up button instead of down, the boy will actually sit in the chair for a few seconds and wait for her to mount him, which is pretty cool.
Also, for certain enemies like wind girl and golem, if you press up for them to release you, and they only release partially and you don't do anything, after a while they will remount you and continue fucking.
I will post more interesting, out-of-the-way stuff as I find them.