The Times of India has a very short piece focused on the relationship between the two gentlemen. Keanu said the following about Mr. Sanada:
…he formed an unbreakable bond with his Japanese co-star while shooting for their upcoming movie, 47 Ronin, and said that he is like a brother to him…
With respect to Mr.Reeves, Hiroyuki Sanada said:
…they prepared dialogue and practiced a lot of fight scenes together, so they shared a lot physically and mentally, which brought them close. He added that Reaves is always very calm and he respects him as an actor and as a person.
The piece is here.