This book is 18+ and has several trigger warnings including, rape, violence, incest, underage sex, self-harm. Please do not read if any of those things make you uncomfortable.
This is Subverse, subverse is like omegaverse but its just like a bdsm relationship and their "secondary gender" is just either sub or dom, its not mentioned much in the book because I know subverse and omegaverse makes some people uncomfortable.