Looking for a story

If it was on Reddit I don't know about it being there because I read this before I join Reddit...

I don't remember everything about the story but it was a brother trying to help a sister get into an all girls style school or something like that, But they had to go through trials of some sort and one of the other girls trying to get in finds out that the brother is better dressed as a girl trying to blend in, she doesn't know the only reason he is there is to help his sister but she hurts his nuts in multiple ways trying to reveal him as a man. But he powers through.

I don't know any more about the story because I never got to finish it and if it's not found no big deal but I'd like to read it and actually finish it this time