Julia is the most popular girl in school by far, coming from a wealthy background, being attractive, charismatic, kind, hardworking and intelligent. She's also quite determined and crafty and can be surprisingly ruthless and scary from time to time. She's always the top of your grade, is the student council president and also very active in the track and field club, gaining the respect of basically the entire student body. Except for you. You come from a rougher background and were always irked by how perfect Julia seemed to be and how easy everything was for her, so you always disliked her a little. And she could sense that, which in turn rubbed her the wrong way. It quickly escalated and the two of you became rivals, always trying to one up each other and compete at every possible opportunity (often to your dismay as you rarely managed to best her).
One day after school, you were caught by Max, one of the boys in your class with a particular big mouth and ego who is crushing on Julia and has always hated your guts for going against her. He cornered you with two of his friends and tried to teach you a lesson, but you didn't go down without a fight and held your own fairly well, actually managing to knock out one of them and give Max and his other friend some nasty bruises. In turn however, you took quite a beating, with a lot of bruises yourself.
You thought about staying home the next day, barely able to get out of bed as your entire body is hurting, but at the tought of Julia thinking of you as weak you grit your teeth and drag yourself to school. You expected Julia to mock you upon seeing your state and braced yourself inwardly upon entering the classroom, but to your surprise, upon seeing you, Julia seemed shocked instead and simply stared at you, not saying anything. The classes pass quickly and as you stand at your locker, Julia suddenly calls out to you with a surprising dark and concerned expression. "Hey. Are you alright? Who did this to you? Tell me their name and I'll make sure to ruin them."