Perhaps what Lin Yao regrets most in his life is hurting someone else's brother and then hurting his younger brother. Perhaps what Xia Ling regrets most is that she set a wrong example for her younger brother and then soft-heartedly agreed to what he said. What both of them don't understand is that they are obviously a fool, how can their thoughts be so complicated, and why can't they live a simpler life.
Conception: