Self defense story

Looking for a story where a young woman attends a self defense class. The detail I specifically remember is at the end of the class the instructor tells the guy she used for practice to relax because she’s done busting him, but when he turns around she pulls his pants down and when he bends over to pull them back up she grabs his balls and pulls them up and between his legs.

Will accept any of your favorite self defense class stories though, especially if the guy is unprotected and busted really hard by the women