Jessica Kiang “Okinawan kindness leaves no one behind!” goes the chirpy sign-off on a political radio commercial halfway through Japanese director Masaaki Kudo’s artful and affecting Karlovy Vary competition title, “A Far Shore.” Already it plays like the bitterest irony. Aoi, a 17-year-old mother working illegally as a nightclub hostess in Okinawa, the poorest prefecture in Japan, listens with a dissociated look in her eyes: She has been left behind by practically everyone, and while Kudo’s film is deeply compassionate toward the struggling, stubborn, subjugated teen, this is an Okinawa of precious little kindness.We first meet Aoi — rivetingly played by Kotone Hanase — at work with her lissome best friend Mio (Yumemi Ishida), also a minor, as the girls giggle, drink and flirt with a couple of guys in town for a good time.