Because the Raen are reclusive and solitary, I needed a reason for Ryuji to go to Eorzea in the first place. I decided that he had a curiosity and wanderlust that didn't quite fit into the rigid social conventions of his people; given the naming conventions, I assumed these to be similar to high-society Japanese social conventions, so that meant that I had to put Ryuji into a higher-class family. I went with merchant, because I didn't want him to be the outright son of a lord. I then needed a reason as to why he would be a Pugilist specifically, which isn't exactly a well-to-do fighting art. Thus, I developed a backstory where he rebelled in his youth by ditching the studies provided by his merchant family, who had little time for their fourth child, and often found himself scrapping with and causing trouble among the disaffected and low-born; thus, Pugilist suits his background.
But I needed a way to get him TO Eorzea and the Pugilist's Guild, so I had him disowned by his father for all the trouble he brought to the family name, only to be picked up as a ward by the governing family of his small town for his curious mind. Here, he was whipped into shape, but was still too unfocused and undisciplined to serve them as a warrior. One of the Hinoto combat masters knew of Hamon Holyfist's reputation and of his less-rigid Pugilist style, however, and suggested that Ryuji be sent abroad, where this foreign fighting style could bring craft to his unpolished street style and bring a unique flavor to the Hinoto name. And so, they sent Ryuji to Ul'Dah and the Pugilist's Guild specifically, and it was in his travels to get there that Ryuji gained disdain for the Garlean forces occupying Othard - but that's a different story altogether.
As you can see, the need to explain those two basic aspects resulted in a massive exercise in extrapolation, and gave me the outline of a character that I can continue to flesh out and develop at my own leisure. And that's with the relatively little that Raen players have to go on! Imagine what you can do with all the tribal and historical Mongolian facts at your disposal!