Arian

A different planet explained by Reiji as the country where he was born.

Introduction
In the third episode of Gundam BF Reiji claimed to be a prince hailing from this different planet after Sei witnessed him teleporting in a beam of light. However, the way Reiji portrayed himself in the story, and the fact there are no known planets other than Earth with life, led Sei to believe it was a badly made up excuse to hide his origins. Further episodes seem to imply Reiji is not an earth being, one such evidence being the fact he had never been familiar to salt water, at the time Mr. Ral considers he could hail from a colony.

Episode Twelve added possible confirmation to the possible existence of Arian and Reiji's status as a Prince. Chairman Mashita, the head of PPSE and organizer of the Gunpla Tournament, recognises Reiji as an older version of an Arian Prince he met in the past. This leads Mashita to actively interfere with the tournament in order to have Reiji removed from it, namely adding a Mega Zaku to the battlefield with orders to destroy Build Strike and actively selecting a Fighter to defeat Reiji on the next round. While his motivations to do so remain unknown, It would seem he fears the prince as someone with reason to have a grudge on him.

Chairman Mashita's knowledge of Arian and Reiji's ability to fight with Gundam Models implies that Plavsky Particles, and thus Gunplas, the Battle System and Gunpla Battle, are actually some form of Arian technology Mashita might have stolen in order to get rich on Earth with the creation of PPSE. However, Reiji has so far not aknowledged the Plavsky Particle as something he is familiar with.