He is so mean to her for no reason.
She always wonders why...
Until one day,

she found him crying and asked what's wrong
boy: "nothing that you can help me with! leave me the hell alone!"
girl: "why do you hate me?"

boy: "I hate you because I can't have you"
girl: "why can't you have me?"
boy: "because I love you too much to accept you being with someone like me."