Future Boy Conan

On Remnant Island, a tiny surviving enclave of humanity on the devastated Earth, Conan lives alone with his grandfather until a young girl, Lana, washes up on the shore. Two soldiers of Industria land their hydroplane and kidnap Lana. While threatening the intruders with a missile, Conan's grandfather is mortally injured when one of the soldiers opens fire on him, detonating the launcher.