Many thanks to Ayako for the link!
Asia One has posted a great summary article on 47 Ronin. They talk about the film and include pieces of interviews from all of the cast members on various topics related to the film. On Keanu Reeves’ speaking Japanese in the film, Hiroyuki Sanada said the following:
“There was one scene where he spoke his lines in Japanese and it made me cry. It was very nice, with a lot of emotion. So I think Keanu did very well with Japanese. His effort to act and do well, it’s very respectable.”
You can read the article here.