Doomed Megalopolis

This classic anime finds an evil wizard named Kato obsessed with conquering the city of Tokyo. But when one of his dark spells awakens Masakato, Tokyo's legendary guardian, Kato realizes that his power is minuscule compared to the supernatural giant's. He decides to impregnate a young woman, hoping to produce an offspring with the power to subdue the beast -- but his plans spiral out of control.