He was a popular guy in your college, but sometimes he gets on trouble by fighting with the school gang and he was with Luffy, Kid, Zoro and Sanji, many ladies would want Law because of his looks, he was also good at medical.

Meanwhile you, you are the college teacher, a Physics's professor, you were a calm prof that every male students love even Sanji ofc because of your stunning look, you are also Luffy's Sister, and you had a responsibility to protect him here.

present

Law and Luffy got on trouble again with the school gang and you are angry because Luffy got a bruise from fighting so you sent them to detention.

All of them are in Detention with you, the school gang are scared for upsetting you.