If you're looking for anime similar to Cosmo Warrior Zero: Hunt for Young Harlock, you might like these titles.
In the early 21st century, a great meteor struck the Earth, destroying everything in its path. Amidst the chaos and destruction, a fleet known as the Trader Force quickly conquered the planet and before long, helped usher humanity into a new dark age. In the present, an ordinary boy named Tetsurou has become involved in the struggle between the invaders and mankind. Now, with newfound powers, two unlikely companions and an otherwordly beauty at his side, Tetsurou must help bring an end to the Trader Force and free mankind forever!
In the distant future, the planets are now connected with a massive galactic railway system. The Galaxy Express 999 has crash landed on a mysterious planet. On board are The Conductor, Killian, Maetel, and Tetsuro, a ten year-old street urchin with a heart of gold. Now it’s up to the SDF Sirius Platoon to rescue them before the Herise Time Mystery—a rift in the deep axis of time and space—repeats.
Maetel abandoned her mother and her home planet, the doomed and frozen La Metal, where people must become cyborgs to survive. When she is beckoned to return, her options seem slim: follow her mother's path (and with it a robot mind and the contempt of all humans), or run away and fight with humans against the machines. Yet, she is not without comrades and defenders. If she can accept the friendship of beings of metal who desire peace, and oppose those who think being made of flesh and blood is enough to make one human, she may still have a chance to find her own path.
While travelling on the Galaxy Express with Maetel, Tetsuro befriends Claire who was forced by her mother to exchange her organic body for crystal glass. When danger threatens Tetsuro, Claire tries to help him.