Due to dangers of decreasing resources and growing pollution, the International Scientific Organization (ISO) is established to improve environmental conditions throughout the world. But an international criminal group, Gallactor, tries to achieve world domination by taking control of the ISO. Gallactor was created by a mysterious being from outer space known as Generalissimo X, who gives orders through its chief commander on Earth, the masked Berg Katse. To fight Gallactor and its robot monsters, the ISO's Dr. Nambu enlists five brave youths into a combat squad called Gatchaman,the Science Commandos. Special scientific powers and dramatic birdlike costumes make the Gatchaman Squad a match for Gallactor, wherever on Earth it may strike. Ken (the Eagle) is the wise leader, assisted by sometimes-foolhardy Joe (the Condor), pretty Jun (the Swan), eager little Jinpei (the Swallow), and strong Ryu (the Horned Owl). Each has individual scientific weapons, but their main power lies in their aircraft, the Phoenix, which can transform itself into a fiery arrow capable of piercing the most massive threats. GATCHAMAN is a series of dynamic action and tension as Ken, Joe, Jun, Jinpei, and Ryu hold themselves in constant readiness to meet each new threat by Gallactor to conquer the world. (Source: Official Site) About Battle of the Planets (U.S.)

After Leader X is seemingly destroyed for good at the end of Gatchaman II, a fragment of him that survived grows and mutates into Z. With the head of the Egobossler family, Count Egobossler (and his two subordinates Mechandol and Kempler), Z is bent on destroying the Earth, and the Science Ninja Team, once more. In the wake of Anderson's death, Dr.Nambu has become the new head of the ISO, while the team is now confined to the Gallatown (aka "G-Town") underwater base. Engineer Kamo is introduced, and after the New GodPhoenix is destroyed early on, the team receives the new Gatchaspartan as their mecha. The Gatchaspartan has a special mode as well, called Hypershoot, that can only be utilized by Ken (with his new "Gatchafencer" sword). As the series progresses, it is learned that the radiation exposure from constant use of the Hypershoot is slowly killing Ken, and that continued use would mean death. Meanwhile, Z plans to destroy the earth with an antimatter asteroid, codenamed "Poison Apple".

Off-duty Japan Self-Defense Forces (JSDF) officer and otaku, Youji Itami, is on his way to attend a doujin convention in Ginza, Tokyo when a mysterious portal in the shape of a large gate suddenly appears. From this gate, supernatural creatures and warriors clad in medieval armor emerge, charging through the city, killing and destroying everything in their path. With swift actions, Youji saves as many lives as he can while the rest of the JSDF direct their efforts towards stopping the invasion. Three months after the attack, Youji has been tasked with leading a special recon team, as part of a JSDF task force, that will be sent to the world beyond the gate—now being referred to as the "Special Region." They must travel into this unknown world in order to learn more about what they are dealing with and attempt to befriend the locals in hopes of creating peaceful ties with the ruling empire. But if they fail, they face the consequence of participating in a devastating war that will engulf both sides of the gate. [Written by MAL Rewrite]

Several months have passed since the infamous Ginza Incident, with tensions between the Empire and JSDF escalating in the vast and mysterious "Special Region" over peace negotiations. The greed and curiosity of the global powers have also begun to grow, as reports about the technological limitations of the magical realm's archaic civilizations come to light. Meanwhile, Lieutenant Youji Itami and his merry band of female admirers struggle to navigate the complex political intrigue that plagues the Empire's court. Despite her best efforts, Princess Piña Co Lada faces difficulties attempting to convince her father that the JSDF has no intention of conquering their kingdom. Pressured from both sides of the Gate, Itami must consider even more drastic measures to fulfill his mission. [Written by MAL Rewrite]