The idea of the series is based on the conflict between good and evil, evil represents the great Vega, an evil space commander who lives in his spaceship in outer space whose goal is to control all the planets of the universe, Vega uses in his attack on other planets robots and huge robots, and one day Vega the Great invades the peaceful planet Fled, but the Duke of Fled, the son of the king of the planet Fled, manages to escape by stealing Grendizer, who was developing on the scientifically advanced planet Fleed and leads Grendizer To outer space until he falls days later tired on planet Earth and is found by Dr. Amon, head of the Space Research Center in Japan, and adopts the Duke of Fled without revealing the truth of his personality and calls him Daisuke, the events of the series begin when Vega the Great prepares his plan to invade Earth and Vega is surprised by the presence of Grendizer on Earth.

The story is in the 18th century in an English coastal area. Jim Hawkins is a thirteen-year-old boy with a pet cat named Benbow, Jim and his mother have been running Admiral Benbow's hostel since his father died in a shipwreck. But their quiet life is disturbed when a drunken sailor who calls himself the captain decides to reside there. A series of horrific events leads to the death of the captain, leaving Jim with a map leading to Captain Flint's legendary treasure. With the help of Dr. Livzy and Mr. Triloni, he prepares a sailing ship and a crew to go in search of treasure. In the nearby city of Bristol, they include one-legged chef John Silver, Captain Smoldt and others. But as the journey begins, Jim realizes that things are not what they seem