I wouldnt say its explicit without the extra chapters but the dynamic is similar. An older man who raises a young boy to be fully dependent on him (knowingly or not idk cuz its up to interpretation unreliable narrator and allat) nut boom the younger dude grows up and is like a total psycho but luo binghe is very adorable. That and the whole take my body make me yours part. Both the tops are unhinged and attention crazy

This is reminding me of The Sum Villain's self-saving system