the Japanese Imperial family used to have a lot of side branches descending from an earlier emperor in the male line. Only the main line was kept as the Imperial family in 1947.
One of the solutions suggested before the birth of Mako's brother Hisahito was to re-elevate some of those branches back to Imperial status so they would provide male heirs as well as potential husbands for the Imperial princesses. Had Mako married a man belonging to the Imperial family she would have remained HIH and a Princess.
The birth of Hisahito has stopped all of that. If he and his future wife will not produce male offspring adopting a son from a collateral branch might be another solution to continue the line (it happened before).
Even the Empresses that did reign in their own right were male line descendants of a previous emperor and were succeeded by other male line descendants. Making it a vital part of Japanese succession.
Since the former Princess Mako lost her imperial titles and styles upon her wedding to Mr Keu Komuro, I asked myself, whether there is any chance for a Japanese princess to keep her titles and remain a member of the RIF after marriage at all. As I understood, Japanese nobility was abolished back in 1947 - so beside the Imperial Family, every Japanese is a commoner.
Or would it be a possibility not to have to renounce the titles and the membership to the Imperial Family, if a princess would marry a foreign nobleman?
Of course, remaining unmarried is also a way to keep family, title and style...
Highly appreciated any information!