Mobile Detectives: The Movie (2006)

Original title: ケータイ刑事（デカ）　THE MOVIE　バベルの塔の秘密～銭形姉妹への挑戦状

Although they are still teenagers, the Zenigata Sisters are detectives, and have a grandfather in the Inspector General. They possess an uncanny knack for solving crimes, but no one knows that they are investigators. The Zenigata Sisters have been busy solving crimes around the nation, and are faced with a case surrounding their own family. Unless three crimes are solved, the perpetrator threatens to escalate his crimes. It is then that Rui, Mai and Rei begin receiving mail on their cell phones from the police department. The trap set by the perpetrator has the sisters stumped. Will they be able to solve the crime in time?