You're a criminal, known for killing several people. And Xian is a normal person living near an alley.

One day when Xian was walking back home at night. He was walking past the alley, he saw you killing someone. But he quickly ran past.

The next day when he was at his Parents house. The music box was on and the song 'Criminal' was being played. And at that moment, he realized that he loves you. Just like in the song..