Stunt pilot Joe Casaca, along with Professor Tobishima, head of the Tobishima team, set out to investigate a gigantic alien ship that has crashed. They discover Rita, very injured inside the ship. The Gailar Empire begins to attack Japan with a robot bomb and Rita says that the only way to stop them is by using the Space Pirate, the ship she came on. She sets off with Joe to show him how to control the ship.
Rita tells her origin, how the Gailarians arrived on Earth and how Geldon started the invasion plan. She also tells of her escape, in which her father would have been killed by the Gailarian soldiers. New robot bomb attacks and is destroyed.
Another attack by a robot bomb, this time in Hokaido. Masato, nephew of Doctor Shimura, sees his parents dead.
Professor Tobishima goes out with Rita at the Red Dragon. They are attacked by a robot bomb, but return to base. Joe, very angry that Tobishima took Rita on the old plane, is disgusted. He even argues with Rita and gives up on Piloting the Space Pirate. Rita sets out to destroy the robot bomb, with Professor Tobishima as co-pilot. He pilots the Pirate jet, but is hit and then parachutes, which is hit as well. Joe saves him and they make amends.
At the base there is concern for Masato, a young man orphaned due to the attacks of the aliens and who now shows aggressive attitudes. Unfortunately, Japan is attacked by a new monster of Gailar and Joe goes out on reconnaissance with his hunting arero. The enemy is too powerful and the young man is forced to make an emergency landing that knocks him unconscious. The hero manages to recover and, with a skillful gunshot, manages to damage the monster enough to put it to flight. Once the enemy who could discover the location of the base has been removed, Rita can intervene with Groizer X and rescue her comrade. The enemy returns to the assault but this time Joe is in command of Groizer X thanks to which he can stand up to him. A long air battle and good triumphs once again over evil. At the end of the adventure Joe and Rita return to little Masato, who will always miss his loved ones but has now found two true friends.
Joe and the professor go to the presentation of a new civil aircraft called Mach 3.5 designed by a brilliant Japanese scientist, Prof. Doyama. The aviation managers decide to entrust the new vehicle to Joe, who will become its first pilot. The Gailarians, hearing the news, decide to kidnap the professor to take possession of his creation. Joe, on reconnaissance with Kaori, Professor Doyama's daughter, discovers the alien attack but too late. The professor has disappeared and the boy ends up in an ambush by two alien soldiers who also manage to kidnap the hostage's daughter. The Gailarians also manage to recover the missing element, i.e. the superfuel necessary for the operation of the Mach 3.5. Rita goes into action with little Tobè who, driving the auxiliary drill of the Groizer X, recovers Joe who manages to destroy the enemy plane.
The Gailarians, to bring Rita back to their side, decide to make a television program with Kento, the girl's first love. The Gailar breaks into a Tokyo television station and orders to broadcast a recorded tape that contains a message from Kento for Rita who, hearing it on TV, is shocked. The stratagem has an effect: the girl, deeply affected by her beloved's speech, takes the Groiser X back to Gailar, her homeland, and reconcile with her people. Joe, determined to reason with his partner, chases the Groiser with a plane from the base but Kento reveals his true hostile nature, shooting down the small terrestrial aircraft. Rita changes her mind and decides not to return to Gailar: Kento then has no choice but to attack the Groiser X. The girl, now determined to defend her new homeland, can only return fire by defeating her compatriot and recovering Joe, who ditched without problems after the accident.
A great Japanese scientist, Professor Oshikava, built a new reactor called V7, capable of amazing performance in the aeronautical field. Joe, a family friend of the scientist, goes to the professor's laboratory to personally test the new device. There he meets Koji, son of Professor Oshikawa, a boy whose life Joe once saved. At the Akane base, the alarm sounds for the sighting of a Gailar monster which, however, suddenly disappears into thin air. Joe, on board his plane, makes a reconnaissance in the area where the sighting occurred and Koji intends to follow his friend but only gets a sharp refusal. For this prohibition, the boy becomes stubborn and to prove his worth, he tries to go to the place anticipating the hero. In the forest, the little boy is kidnapped and hypnotized by a Gailar commander so the next day Koji, surprising everyone, steals the plans of the V7 reactor conceived by his father.
General Dogar orders Admiral Haruk to use his Viking underwater space robot to capture the Shark spaceplane and take Joe hostage. Dogar's strategy is successfully implemented and Haruk, despite having been the greatest friend of prof. Yan is forced to use the despicable weapon of blackmail by ordering Rita to return Groizer X and submit to the justice of the Gailarians. Rita, however, opposes the attacks of Dogar's spaceship and so the evil Gailar general orders Haruk to kill Joe. Surprisingly, Admiral Haruk frees Joe: his code would never have allowed him to disobey orders but his morals did. In a last act of heroic courage, Haruk sacrifices his life in the name of friendship: not even the cruelties of a war can erase such a noble feeling from the soul of a good man.
Isamu Okamoto, an old friend of Joe's and a very skilled student pilot of Professor Tobishima, arrives at the Akane base. After a pleasant evening with the base team, the boy returns to Hokkaido where his base is stationed but his plane is captured by the Gailarians who use him as a guinea pig for an experiment to modify brain cells, in order to enslave the human race. Isamu becomes a slave in the hands of aliens who send him on a mission against a military airport where he makes a real massacre. Since the test was successful, the boy is assigned to another mission and right at the airport where he served, killing his former companions. At the Akanè base, the alarm goes off and Groiser X goes into action, soon clashing with the enemy. Joe and Rita discover that the pilot of the enemy ship is Isamu who does not seem to recognize them. The pilots, distracted by the incident, are captured together with the Groiser who is forced to land.