Tbh if you didn't see that vicious cycle coming back around at the end you weren't paying attention (or perhaps haven't lived enough of real life). This is not a happy ending. None of these characters were innocent victims in this whole thing and that's what makes this such an honest representation of toxic relationships and how suffocating they can be. They were all manipulating each other and not communicating their feelings clearly. I probably wouldn't read this again but I think it's a unique find in the BL world and worth a read (in the correct mindset).
My Lover, My Teacher