When I watched G Gundam I was confused by my inability to pick out why Domon Kasshu should be Japanese. The other Gundam Fighters take on national characteristics, after all. He could, I suppose, be a ganbariya-san but I’d say every G character is that (including the villains and the horse). Then again, British novels about Brits interacting with foreigners don’t emphasise their heroes’ Britishness, they emphasise their heroes’ normality (as a contrast to Johnny Foreigner’s amusingly weird traits), so perhaps something similar is happening here. Or maybe I just missed some obvious clues.
Domon’s status aside, if someone were to ask (like Zero in the eighth episode of Geass R2) where the ‘Japaneseness’ in G Gundam is, I’d point to Rain.