Apr 1, 2021 Quite a few Japanese films serve as an extra episode of a popular TV series. They even get their own abbreviation: “SP” (special program). Those who venture into these SPs unacquainted with the world of the TV show can feel as though they’ve crashed a family dinner. Fortunately, “Signal The Movie Cold Case Investigation Unit,” a cop actioner that is the film offshoot of a 2018 Fuji TV series that was itself based on a 2016 Korean show, provides a rapid-fire digest in the opening minutes to get the uninitiated up to speed. But an investment in the characters is still assumed, which is not surprising for a film targeted at core “Signal” fans. The personalities of the main cast, which range from the spit-flecked emotional (Kazuki Kitamura) to the clenched-jaw stoic (Michiko Kichise), are carryovers from the show, though director Hajime Hashimoto, a veteran of the long-running “Aibou: Tokyo Detective Duo” TV and film series, is new to the “Signal” team.