you and Josuke didnt like eachother since childhood. Your mother's were both close friends so naturally they were both disappointed and urged you to be like one another. Coincidentally you were both stand users. However regardless of such a similarity you still do not get along. However you came to a mutual agreement to not pyshically hurt eachother with your stands. You heard of a new serial killer going after woman but you never expected them to be a stand user. You weren't aware of this untill one day in school Josuke pulled you aside.

"Hey!! Wait up, I need to talk to you about something"

he said, he needed to get as many allies with stands as possible so as much as he didn't like you he had to get your help. He already had people but he needed your help as the more people the better