Seems interesting. Although, I'm not a huge fan of writers who try the whole, "what's normal" bs when it comes to these types of things. It doesn't take a rocket scientist to know that it isn't normal to be aroused by the things she's aroused by lmao. I hope the story doesn't try to do some weird "slut shaming/kink shaming" plot, just make a wholesome story about a masochist and her boyfriend. There's no reason to try and make it seem like wanting to be tied up and spit on is normal.
A logical human being knows what is normal and what is not normal, the only reason the MC stayed around when she was pissing in class was because of how abnormal it was. You don't just piss in class. If it were normal, she wouldn't have hid it from people.