Mu Jin was very dissatisfied with Gu Yan becoming her deskmate, because he happened to see her fall into embarrassment while imitating "Peppa Pig". When he arrived at school the next day, he saw Gu Yan looking at him with the eyes of caring for "children" with intellectual disabilities. Then Mu Jin's violent temper supported him and Gu Yan to fight for a lifetime.
Purpose: Mu Jin is the person Gu Yan identified when he was young and will never change in his life.