One day, Yume, a kind older sister who cares for her younger brother, finds out that he is being bullied at school. Wanting to help him, she disguises herself as a man and sneaks into the boys' school where her brother attends. She tries to stop the bullying by finding out the weakness of the main bully, but ends up discovering her greatest weakness: that she is a girl. She immediately becomes the prey of savage men and begins a nightmarish gang rape routine.