The book only touched briefly on Wu Chen's past, mentioning his difficult childhood: an abusive father, a mother who fought just as fiercely, a home on the brink of collapse, and the broken boy he became.
When he first appeared, he saved the heroine from a horde of zombies. However, he didn't become her companion, only because he was keeping a disfigured, squat zombie.
He couldn't integrate into human society.
Wu Chen chose to wander with the zombie.
The heroine had once asked him who it was.
He said it was his adoptive mother and that he wanted to keep her until she rotted away completely.
That zombie also had a spark of sentience and would only eat other zombies.
Unfortunately, the heroine had exhausted her healing superpower to save her own life, and it had vanished.
The heroine promised him that if her healing superpower ever returned, she would try to help cure his adoptive mother.
