When they were younger, Lucy was socially isolated, which led to her developing her Tsundere personality. Mike, on the other hand, doesn't appear to have faced as many issues while growing up, and turned out to be a Nice Guy. However, thanks to their friends laughing off Lucy's abuse and treating him poorly, he has grown bitter and cynical. This has only grown worse after their friends learned that he rejected Lucy's confession -- he's even been explicitly told that his Long-Distance Relationship with Sandy 'doesn't count' because "those never work out", and that he should hook up with the girl who's right there, despite how she used to treat him so badly.