Kenta Fukasaku follows up the widely reviled Battle Royale II with this cartoonish adaptation of the popular 1980s television series Sukeban Deka (translation -- delinquent girl cop), based on a popular manga which also inspired an anime series. Yo-Yo Girl Cop has its moments, but it should be a lot more fun than it is. After all, it's about a gorgeous young woman who goes undercover as a schoolgirl and uses a yo-yo as a weapon. Featuring a cast of J-pop stars and an amusingly gruff Riki Takeuchi as Kazutoshi Kira, Saki Asamiya's (Aya Matsuura) boss, the movie gets bogged down in teen angst. Some of this works. Saki's visit to Kira's rundown apartment, for example, strikes just the right mix of humor and pathos. But then there's the overly long expository text-messaging/music-video interaction between shy bullying victim Tae (Yui Okada) and Saki, and a couple of key plot points severely strain credulity. The filmmakers spend an inordinate amount of time on the relationships between these characters, so it's disappointing when they later behave in totally incomprehensible ways, as is the case with Saki's apparent attraction to the strange sociopath Jiro Kimura (Shunsuke Kubozuka), and with Tae's emotional manipulation at the hands of the sinister Jiro and turncoat yo-yo cop Reika (Rika Ishikawa). These plot developments certainly detract from the film's "girl power." That said, the action, when it comes, is unconvincing, but fun. The penultimate battle, between leather-clad yo-yo cops, is a hoot, and Matsuura (known as "Ayaya" to J-pop fans) demonstrates serious star potential as the stone-faced, foul-mouthed heroine.