I think there are as many Filipinos outside the Philippines as there are inside... the government has a policy of trying to send as many people abroad, skilled or otherwise. Also Filipinos are the second biggest foreign minority in Hong Kong (after Chinese born outside HK but ahead of British and American) and are also very numerous in Japan and South Korea.
Which leads me to suggest this country could have a strong Filipino minority (say 80% Japanese, 15% Filipino, 5% others).
They could be fighting for equal rights, equal wages, equal opportunities (including career advancement); they could also be demanding to be recognized within the constitution as a distinct group; the idea pushed further, 80% of this minority group could be located in a few districts or provinces and demand scesesion (similar to the Malanje in Cyberia or the Bloc in Canada).
Or they could be all over the place, like American and Canadian aboriginals or some immigrants group in Europe and North America, therefore unable to gain any seats all by themselves yet still representing a strong block of voters which leaders of the two main parties could aim for, Filipinos being mainly immigrants, would be a bigger influence in bigger towns.
Or something in between, like Hispanic people in southern USA, pretty much stread out yet much more influent in some areas (say Texas) rather than others (say North Dakota)....
Just an idea.