Takanoha High seems like your ordinary school for children of wealthy families, but in reality, it is ruled with an iron fist. A society of criminals hides under the guise of a high school and is headed by the Mizuchi family. Takada Mizuchi, the father, has great influence over many organizations, including the local police. The three Mizuchi sisters head the criminal activity, extort money, and hand out grades based on bribes. Students are ranked by their families' financial and social status.
Everyone in their school admires the powerful Mizuchi sisters. First, there is Remi Mizuchi, who will eventually take over her father's position. Her beauty is greatly admired. Ayumi Mizuchi cares only for money. "You can always buy fame." Emi is an artist of only fair talent. She uses the influence of her family to make her seem like the best around.
The ineffective police have someone in mind to infiltrate this crime organization -- a criminal by the name of Saki Asamiya. Faced with the decision of aiding the police or allowing her criminal mother to be executed, Saki decides to cooperate. Thus, Saki is sent back to her old high school, Takanoha High, where she was a feared bully.
The action in this series is excellent. The fight scenes are full of spectacular animation. The characters are well-designed, and the show makes you forget that it's a bit unusual that Saki uses a yo-yo for a weapon. It is also humorous at times. Check this one out.