Crossbone takes place ten years after Mobile Suit Gundam F91, and multiple characters from that movie return as main characters within the manga. Aside from fan translations, the manga has never been officially distributed in English.
Universal Century (UC) 0133. Ten years after the events of the Cosmo Babylon Wars depicted in F91, 13 year-old protagonist Tobia Arronax/Tobias Allonax is a transfer student from Earth heading to the very affluent Jupiter Empire colonies aboard the Smashion Jovian transport ship. When space pirates of the Crossbone Vanguard attacks the Smashion with their ship, the Mother Vanguard, Tobia willingly sorties out in a Jovian Batara mobile suit holding them off as if he were a natural pilot. Unfortunately, he is captured by Crossbone Vanguard ace pilot Seabrook Arno, who has changed his name to, fittingly enough, Kinkado Now-(note: a Kinkado is a small rare bird)Kincaid Nau and brought before their leader Berah Ronah, who offers him a choice: either head straight to Jupiter and forget what has happened or join them to discover the truth. Tobia hesitantly joins with the pirates, but little does he know the Vanguard's agenda is one of resistance than of piracy.
In reality, the Jovians have been secretly building up their military for years, forming the Jupiter Empire, with the goal of Earth Sphere domination. Their ruthless leader Crux Dogatie maintains a façade of partnership with the Earth Federation, so as to avoid suspicion by the Federal government. Learning the truth, Tobia allies with the Crossbone Vanguard, and under Kincaid's tutelage, becomes one of their most prominent pilots, while using the XM-X2 Crossbone Gundam X-3, while slowly developing his Newtype abilities.
- Tobia Arronax (トビア・アロナクス Tobia Aronakkusu?) : A young boy originally from Earth, as well as the main protagnoist. After arriving on Jupiter along with a group of exchange students from Earth, he becomes wrapped up in the Jupiter War after the new Crossbone Vanguard attacks his ship, causing him to hijack a Bataras mobile suit before encountering Kincaid in the Crossbone X-1. After then finding poison gas containers on board the ship he is attacked by Prof. Karas, an agent of the Jupiter Empire who had originally posed as a teacher for Tobia, only to be saved by Kincaid. Determined to help bring an end to the war, Tobia is often short tempered, letting his emotions get the best of him in battle, while Kincaid continues to help him. Pilot of the Crossbone Gundam X-3.
- Kincaide Nau (キンケドゥ・ナゥ Kinkedu Nau?)/Seabook Arno : Former pilot of the Gundam F91, who was presumed dead after a terrorist attack on a Crossbone Vanguard ship in UC 0128. Ten years after the end of the Cosmo Babylonia war, he and Berah Ronah have formed a new "Crossbone Vanguard" in the form of a group of Space Pirates determined to fight the Jupiter Empire in an attempt to protect earth. After saving Tobia, he begins to serve as his mentor, helping him to become a better pilot.
- Berah Ronah (ベラ・ロナ Bera Rona?)/Cecily Fairchild : Daughter of Corozzo Ronah, leader of the first Crossbone Vanguard, as well as the granddaughter of Vanguard founder Meitzer Ronah. After the collapse of the original Crossbone Vanguard, she, like Seabook, had been presumed dead in the UC 0128 incident. In truth, Berah survived, and learned of the Jupiter Empire's plan to conquer Earth. Determined to put a stop to this, she and Kincaid formed the new Crossbone Vanguard, with Berah as Captain of the ship Mother Vanguard 2. Kind, calm and a skilled commander, Berah still cares deeply for Seabook. Has a pet, mechanical parrot named Haro, which often squaks out references to past events within the Universal Century (even calling Berah "Miss Matilda" on occasion), suggesting that it may have originally been Amuro Ray's Haro.
- Bernadette Briett (ベルナデット・ブリエット Berunadetto Burieto?): A young girl who, after arriving on Jupiter at the same time as Tobia, later stows away on board the Mother Vanguard. Kind, quiet, and highly concerned for Tobia's safety, she reveals that she wishes to visit Earth, as it was the birthplace of her mother. Bernadette later reveals to the crew of the Crossbone Vanguard that she is, in truth, Tetenith Dogatie (テテニス・ドゥガチ Tetenisu Dugachi?), daughter of the Jupiter Empire's leader, Crux Dogatie.
- Zabine Chareux (ザビーネ・シャル Zabīne Sharu?): Former captain of the original Crossbone Vanguard, as well as Kincaide's former rival. Pilot of the Crossbone Gundam X-2, he still holds a grudge against Kincaide, and often shows a lack of trust in him. In truth, Zabine plans the revival of "Cosmo Babylonia", feeling that Berah's "new" Crossbone Vanguard goes against the original Vanguard's ways.
- Crux Dogatie (クラックス・ドゥガチ Kurakkusu Dugachi?): Leader of the Jupiter Empire and father of Tetenith. Ruthless and cunning, Dogatie plans to strike the Earth under the guise of a "peaceful" nation.
Crossbone Gundam had two sequels:
'Mobile Suit Crossbone Gundam: Skull Heart (2003), a single volume of short stories written by Yuichi Hasegawa, placed three years after the ending of Crossbone.
Mobile Suit Crossbone Gundam: The Steel Seven' (2006). A several-volume story which takes place shortly after Skull Heart.
Crossbone Gundam in Other Media
The characters and mecha of Crossbone Gundam often appear in the SD Gundam G Generation video game series, although generally serving as extra content. The series also appears in Super Robot Wars Alpha 2, part of the long-running Super Robot Wars franchise; it is the first non-anime series to be given plot significance in a Super Robot Wars game. Recently, Crossbone Gundam has been announced to appear in Another Century's Episode: R. In these game appearances, Tobia is voiced by Kappei Yamaguchi.