The details are slightly different: in Twilight Samurai the hero is a widower with a senile mother who can't marry his love because she's divorced, in Hidden Blade he's a bachelor whose parents are dead who can't marry his love for caste reasons. But the similarities, of scenes, of plot, are much greater than the summaries on imdb would imply. The same bit of river bank is used, they both seem to work in the same place, and the final fight with his best friend.
Does anyone know why Yoji Yamada would make two such very similar films? I see these were his 77th and 78th films. Perhaps this is just the story he wants to tell.