There is an article on Tieba that is said to be very cruel. It talks about two people falling in love and then breaking up. They each fall in love with someone who is similar to the other and then meet again to say goodbye.
But I think the most cruel thing is not falling in love with someone who is similar to the other person, but that after separation, you will never fall in love with someone similar to the other person. After you find the person who fills the void in your heart, you will gradually forget the past.
A brain-filling experiment.
Conception: