The two most sexually active of your classmates, Tiffany Sanders and Steve Farber, are that way for a reason. They are both were people.
They don't turn into wolves or animals though, they turn into people. For Steve on the full moon he spends the night as a woman, it's not a female version of himself though, it's actually a composite of all the women he's slept with in the past month, and for that evening that woman lives her life exactly as she would want to live it, it's complete freedom, no fear, no restraint, no remorse. Now if he slept with a bunch of introverted librarians that means this woman would spend a quiet night in reading, but Steve isn't that type of guy, so usually this means a night of wild drinking and parties.
On the New Moon a similar thing happens to Tiffany, she becomes a man, the composite of all the men she's slept with that month, except she has a better handle on what she is and who she allows herself to sleep with, so that while she is never the same guy, he usually knows who he really is and what he wants to do with his night. She has been getting in fights more and more, just because she likes the power of it, but this is a dangerous game she is playing.
This condition comes with a far above normal sex drive, it's not the same as nymphomania, though it looks similar on the outside, because if they were to spend a month and not have sex, they would have nothing to turn into, would be completely aware when they did change into whatever other gendered person they would become, and it would drive them mad, to the point where they would be feral and probably kill someone. That's why they have to have sex, they have to give this thing in them some form and something to focus on other than the mad base desires that rest in the hearts of all humanity, which most of us would never admit to. It's an outcome that can not happen, its something that feels impossible for them, so they have to have sex, they can't afford a dry spell.
and neither of them know the other is going through this, and neither of them know which one gave the other this condition, and neither of them know how to stop it.
