this was inspired by a fanfic i once read but imagine a reader who's reluctantly entering a poly relationship with this two men because you're in love with the top but the top is in love with the bottom. the bottom is known for his open-minded and outgoing personality and upon knowing that you are in love with the top, he proposed for you to enter a poly relationship with them. the top, doting as he is, allowed, and you just reluctantly accepted the offer bc you love the top so much.
the yandere in this story is, of course, the bottom. he took this chance to make you fall for him, showing you that he can be better than the top. he played the perfect, nice guy at first but one can see his subtle possessiveness towards you when he always proposed to be in the middle during their smexy session (the reader, underneath him, and the top, on top of him) this annoyed you bc you wanted to be embraced by the top, not him! you foolishly assumed that the offering for you to enter a poly relationship with them was just fake, the bottom just want you to see that you could never snatch the top from him.
then let's say the bottom's schemes worked and you suddenly found out that he's not that bad. as you started to truly become immerse in this poly relationships, the bottom started to drug the top, causing him to become short-temper and abusive. the bottom willingly took the hit, saving you time and time again each time the top almost beat you up.
in the end, you decided to leave the man you used to love and run away with the bottom. the bottom, brattered and bruised, remained content in your arms as you cried and comfort him that this time, you will protect him.
the bottom will give you the illusion of being a savior, and he is willing to take as many hit as it took to make you favor him more than the top, and the top will forever be the villain in this love triangle. it took him quite a long time but in the end, you're his alone.