Gigantor 28

The movie centers on Shotaro, who is living in the modern age with his widowed mother. Tetsujin 28 is accidentally discovered, and Shotaro's mother explains that it was left for Shotaro. He, with the help of Chief Otsuka and an older female classmate, learns to control Tetsujin. In the meantime, a Dr. Reiji Takumi activates Black Ox and plans to attack Tetsujin. (Wikipedia)