Galaxy Express 999: The Movie (1979)

In a world where humans can achieve immortality by replacing their bodies with robotic ones, a young boy named Tetsuro Hoshino embarks on a journey aboard the Galaxy Express 999, a train that travels through space. His goal is to obtain a mechanical body for himself and avenge his mother's death. Along the way, he encounters various individuals with their own stories and struggles, all while exploring the vastness of outer space.