Mitsunobu Kaneko

Narumi, a man out for revenge with the powers he received and a bit of help from the one who saved his life, he creates the persona of Skull Soldier and attempts to discover who really killed his sister.

Keizo Tsujiguchi believes his wife Natsue was having an extramarital affair when their child was kidnapped and killed. He believes of her extramarital affair she was unable to watch over their child properly and blames her for their daughter's death. To exact revenge on his wife, he then adopts the killer's child without telling the truth to his wife or their newly adopted child.

Earth is invaded by an interstellar terrorist group, Big Fire (the Gargoyle Gang in the American version), led by Emperor Guillotine who spends most of his time in a multicolored space ship hidden at the bottom of Earth's ocean, from which he issues his orders. Big Fire is capturing scientists to create an army of monsters to conquer Earth. A boy named Daisaku Kusama (Johnny Sokko in the American version) and a young Unicorn agent named Jūrō Minami (Jerry Mano in the American version) are shipwrecked on an island after being attacked by a sea monster and subsequently captured by Big Fire. They flee to where a Pharaoh-like giant robot is being built by captive scientist Lucius Guardian, who gives Daisaku and Jūrō its control device. Guardian helps them escape before he is shot to death; before he dies, he triggers an atomic bomb which destroys the base. The radiation activates the robot, which now obeys only Daisaku.

Join Daisaku Kusama and Giant Robo as they battle the interstellar terrorist group Big Fire.

Akuma-Kun (devil's child) is a young boy who teams up with Mephisto, an old pointy nosed Tuxedo wearing demon who has a bump on his head. They are both working for Dr. Faust, who control Mephisto by using the solomon's flute. They battle monsters and ghosts.