Invasion of the Neptune Men.

Astronomer Shinichi Tachibana has a secret identity as the superhero "Iron Sharp" and is well beloved by children. When they are attacked by a group of metallic aliens, Iron Sharp drives the aliens away. The resourceful Tachibana helps develop an electric barrier to block the aliens from coming to the Earth. After several losses by the aliens, they announce that they will invade the Earth, throwing the world into a state of panic.