Thanks to Duncan (who has a pretty rad blog you all ought to check out) for plucking from the annals of the internet this explanation of Rose and Camellia from a forum poster who can read Japanese:
"The plot, according to the text below the game, is that the player girl is a commoner who marries into a noble family. One day after the marriage, her new husband breathes his last -- but the pampered harpies running the House refuse to give this low-blood the honor that is her due. There is only one way to resolve the matter!"
Aha, I see. Well, now we've got to play it; a fragile young widow's dignity and inheritance is at stake!