In the manga, Ryoma (called "Ryou" for short in the Manga and TV anime) is an aggressive and short tempered martial artist who crashes a martial arts tournament, then challenges and quickly knocks out most of the students with his more brutal martial arts style. His abilities and durability catch the attention of Professor Saotome, who is looking for suitable pilot candidates for the Getter Machines. To further test Ryoma's abilities, Saotome hires three highly skilled assassins to hunt down and try to kill Ryoma. Ryoma manages to defeat them while trying to resist the effects of a highly potent tranquilizer shot into him by one of Satome's assistants, before finally being rendered unconscious by a combination of fatigue, the tranquilizer, and Saotome humorously tapping Ryoma on his head with one of his wooden sandals. Ryoma wakes up at the Saotome Research Lab, where he is told that the fight before was a test to determine whether or not he had the exceptional capabilities required to handle the Getter Robo, and is given the offer to be one of its pilots. He is made the pilot of Getter Eagle/Getter 1
In the TV Anime, Ryoma is much less aggressive than his manga counterpart. He goes to high school with Musashi, Hayato, and Michiru. He travels to the Satome Research Institute on the day the Prototype Getter Robo is being tested. He witnesses the death of the Prototype Getter Robo team including the son of Professor Saotome at the hands of the Evil Dinosaur Empire. He enlists the aid of Musashi Tomoe and Hayato Jin in order to pilot the real Getter Robo. Ryoma piloting the Getter-1 is key to battling the Dinosaur Empire. Ryoma and his friends fight the Dinosaur Empire until the final battle in which Musahi gives his life to defeat them.
Even after the defeat of the Dinosaur Empire, a new threat arises in the form of the Clan of the 100 Demons. The remaining members of the Getter Robo team get Benkei Kuruma to pilot the last jet of the Getter Robo G. Ryoma pilots the Getter Dragon in the second series.
In the 1998 OVA series Getter Robo Armageddon, Ryoma was framed for the murder of Dr. Saotome. After a resurrected Dr. Saotome threatens to destroy the world, he is released from jail to commit the very murder he was accused of. Ryoma holds a grudge with Hayato; who not only committed the murder of Saotome, he also testified against him. After failing to stop a nuclear attack on Shin Dragon, he vanishes from Earth. He reappears 13 years later in an abandoned base located on the Moon. He rejoins the fight against The Invaders piloting a customized Getter, the Black Getter.
Ryoma appears as a supporting characters in Shin Getter Robo vs Neo Getter Robo. Mentally scarred after being tortured by the Dinosaur Empire and the death of Musashi, he quits the Getter Team and wanders Japan as a martial artist. He returns and helps the New Getter Team when the Dinosaurs Empire attempts to destroy Shin Getter Robo.
Hayato Jin (神隼人,Jin Hayato?) Voiced by: Keaton Yamada - The aloof and seemingly anti-social Hayato Jin, displays considerable skill at various sports, but generally likes to be left alone. Despite this he eventually gets all the girls, including the Kyoryu Empire android spies. Hayato pilots the Jaguar Machine into battle with Ryoma Nagare and Musashi Tomoe. When combined with the others he pilots Getter 2. The machine reflects Hayato's physical strength and speed. He is voiced by Keaton Yamada, who eventually became the voice of Combattler V's Juzo Naniwa. In Getter Robo Armageddon, Shin Getter Robo vs Neo Getter Robo, and New Getter Robo, he is voiced by Naoya Uchida. Getter Robo G was called Starvengers in the US and Hayato Jin was changed to Paladin Spencer.
Musashi Tomoe (巴武蔵,Tomoe Musashi?) Voiced by: Toku Nishio - A Judo expert, pilots the third robot. In the manga, he takes over the role of piloting the third jet and robot, despite failing at all the given physical and mental tests. He is known for dying in almost every series he is in.
Benkei Kurama (車弁慶,Kurama Benkei?) Voiced by: Jouji Yanami - A baseball player, pilot of the third robot in the second series. In Getter Robo Armageddon, he is the adoptive father of the amnesiac Genki Saotome.
Professor Saotome (早乙女博士,Saotome-hakase?) Voiced by: Kousei Tomita - Inventor of the Getter Robo. In the original manga he initially piloted the third jet himself, only to have Musashi forcibly taking over the role from him.
Michiru Saotome (早乙女ミチル,Saotome Michiru?) Voiced by: Rihoko Yoshida - Professor Saotome's beautiful and strong-willed daughter, pilots a jet of her own which doesn't combine with the others, but resupplies fuel and energy. All four of the Getter Robo/G pilots have shown an attraction towards her at some point, though her feelings do not appear to be mutual, and rarely anything ever comes of their advances towards her. Despite this, she remains on a friendly basis with all of them. She is killed before the events of Getter Robo Armageddon, and her death is a key plot point in the series. In the New Getter Robo OVA, she appears to be older and has a much shorter temper than any of her previous incarnations.
Genki Saotome (早乙女元気,Saotome Genki?) Voiced by: Hiroko Kikuchi - Professor Saotome's son, the child tagalong present in nearly all 1970's Japanese action cinema.
In the Getter Robo Armageddon OVA, Genki is a girl, and Professor Saotome deliberately raised her as a boy to mislead the public about her true gender for her own protection. She is left in an almost autistic state after seeing the true cause of Michiru's demise, and then stumbling on to the scene of her father's "murder" some time later. After witnessing "Armageddon", which her father put into motion, the excessive mental trauma causes her to go amnesiac. To protect her from the vengeance of the other survivors, Benkei uses his knowledge of her true gender and her newly amnesiac mind to convince them that she is his own daughter, giving her the name Kei Kurama. Thirteen years later, Kei grows up into a tomboyish and somewhat short-tempered woman, and she becomes one of the members of the new Getter Team, piloting the Shin Jaguar/Shin Getter 2.
Emperor Gore (帝王ゴール,Teiō Gōru?)Voiced by: Hiromu Jin - The supreme commander of the Dinosaur Empire. In the second volume of the original manga, Gore was abandoned by his people when they are forced to return to the earth. In the manga he decided that he will die honorably by battling Getter Robo, however even this chance was stolen from him when a Hyaki empire mech opened fire on his ship, killing him. In the anime he, along with the rest of the empire, died when Musashi crashed the Command Machine into the Mighty Battleship Dai.
General Bat (バット将軍,Batto Shōgun?) Voiced by: Kenichi Ogata - Emperor Gore's field commander.
Chief Gareri (ガレリィ長官,Garerii Chōkan?) Voiced by: Keaton Yamada - Emperor Gore's chief of engineering and designer of mechasauruses. (In the manga it was stated he was the Prime Minister of Science).
Great Demon Yura (大魔人ユラー,Dai Majin Yurā?) Voiced by: Kouji Yada - Emperor Gore's master, very little is known about this very tall demon aside from being a member of the One Hundred Demon Empire that appears in Getter Robo G. Has the power to manipulate the ground to his will.
Chiryu Clan (Volume 2 chapter 8): members of this clan were sent to destroy the Getter robo. the members were Dera (who has a blade on the spine and can spin fast enough to dig through the ground); Garo (who can extend his middle horn to stab his opponent, has two brain, two hearts and six lungs, giving him the ability to revive.); Neon the leader and three others. All born into the Chiryu clan are born with mysterious power. They are considered outcasts even by the Dinosaur Empire. They see the war as a chance to move the chiryu clan up in the Dinosaur Empire.
Mechasauruses (Appear in every episode): All Mechasauruses in the series are capable of surviving in magma and those without requiring to flight can burrow very fast; however, as demonstrated in episode 16 with Geru, mechasauruses cannot survive in magma if it moves on them with enough force to cause an eruption.
Emperor Burai: The emperor of the Hundred Demon Empire (or Hyakki Empire for shot).
General Hidler: Burai's field commander that resembles Adolf Hitler.
General Goller: Burai's chief engineer and designer of the mecha oni.
Mecha Oni (Appear in every episode): The mecha oni are the primary war machines of the Hundred Demon Empire, being much stronger than the mechasauruses and like them often burrow unless they can fly. With few exceptions all mecha oni are named after and resemble their pilots. It is stated and proven in a few episodes that destroying the horn will critically weaken if not destroy a mecha oni.
Go Ichimonji(一文字 號,ichimonji gō?, played by Takeshi Kusao): The 17-year-old main pilot of the Getter.
Sho Tachibana(橘 翔,tachibana shō?, played by Yuko Kobayashi): The 16-year-old daughter of Doctor Tachibana and sister of Shinichi. After her brother dies and the Getter is improved, she becomes another pilot of the robot.
Gai Daido(大道 剴,daidō gai?, played by Akira Kamiya): The third pilot of the Getter. A 17-year-old man, he is the most prudent and conscious of the three. Before becoming a pilot of the robot, he was the pilot of one of the helicopters which helped the robot.
Doctor Tachibana(橘博士,tachibana-hakase?, played by Ichiro Nagai): The head coordinator of the Getter Robot project and father of Sho and Shinichi. At first, he is reluctant to use Getter Robot as a weapon until his son dies.
Shinichi Tachibana(橘 信一,tachibana shinichi?, played by Toshio Furukawa): The son of Doctor Tachibana and brother of Sho. A helicopter pilot of the Getter squadron. In order to help Getter defeat a Metal Beast, he sacrifices himself. It is his death which prompts Doctor Tachibana to change the robot into a combat weapon capable of transforming in different forms.
Yuji Muto(武藤 由自,mutō yūji?, played by Junichi Kanemaru): The informatics and programmer expert of the Getter squadron, who works mainly at the base of the NISAR. He is also the pilot of the flying ship which transports the Getter Robot after its battles.
Lee Foa May(リー・フォア・メイ,rī foa mei?, played by Eriko Hara): A nurse at the NISAR who treats the pilos and has a special relationship with Go.
Dr. Pochi(Dr.ポチ?, played by Masaharu Sato) & Dr. Tama(Dr.タマ?, played by Isamu Tanonaka): The assistants of Doctor Tachibana and the main comic relief of the series.
Doctor Yoshii(吉井博士,yoshii-hakase?, played by Kohei Miyauchi): A scientist who collaborates in the Getter project.
Remi Yoshii(吉井レミ?, played by Miyako Endo): The son of Doctor Yoshii.
Akira Daido(大道 哲,daidō akira?, played by Chie Sato): The younger brother of Dai.
Okada(岡田?, played by Yuki Sato): One of the candidates to become a pilot of Getter.
Nakano(中野?, played by Taiki Matsuno): One of the main mechanics in the NISAR base
Professor Randow(プロフェッサー・ランドウ,purofessā randō?, played by Daisuke Gori): A preeminent scientist in robotic engineering who wishes to conquer the world.
Baron Yasha(ヤシャ男爵,yasha-danshaku?, played by Masaharu Sato (older brother) and Michihiro Ikemizu (younger brother)): A strange being which has a body with two heads, one blue and one red.
Count Rasetsu(ラセツ伯爵,rasetsu-hakushaku?, played by Michiko Abe (female) and Ichiro Nagai (male)): A servant of Professor Randow and a cloned being. It often is at odds with Baron Yasha for Yasha's lack of ability in battle. It has a male face in its breast.
Viscount Narukisu(ナルキス子爵,narukisu-shishaku?, played by Ryo Horikawa)