Sukeban Deka - S01

After spending time at a juvenile corrections facility, teenage delinquent Saki Asamiya gets a chance to redeem herself and delay her mother's possible death sentence by working as an undercover cop. Armed with nothing but a special yo-yo, Saki's assignment is to return to her high school and investigate the corruption and mysterious deaths among the students. But to find the answers to what's happening at her school, she must confront the wealthy and powerful Mizuchi sisters, who moved in and took control after her previous expulsion.