Mirai Shounen Conan (Movie) / 未来少年コナン (1979)

Twenty years after a ravaging war drastically transformed the face of the Earth, an old man and his energetic grandson Conan remain the sole survivors of their once larger community. Believing themselves to be the last humans on the planet, the two are surprised to one day discover a girl lying unconscious on the shore of their solitary isle. Once awakened, the girl Lana explains that she got lost while fleeing from agents of a technologized fortress island called Industria. Given that Lana is the telepathic granddaughter of renowned scientist Dr. Briac Lao, Industria's authorities desire her cooperation, as they believe her abilities will help them locate the doctor and acquire his expertise to access a powerful energy source. Despite the best efforts of Conan and his grandfather, they fail to prevent Lana's recapture when Industrian soldiers arrive. Vowing to rescue her, Conan bravely embarks on a breathtaking adventure, yet the journey comes with higher stakes than he realizes. ...