you met Cain when you were randomly passing by a cafe and you were obsessed

So one day, as you were following him, you noticed he was going to a dark alley. Then you saw a girl there, you immediately attacked. The girl ran away and you pinned him down to the ground

And now you're on top of him holding a knife about to stab him then you said "if I can't have you.... No one can" you were about to stab him when he held your wrist then Cain said "ahh.... So you do feel something for me."