I think the lone Samurai is Hiro's dad. I am mainly basing this on the fact that the actor who plays his dad has very distinctive/intense eyes and so did the the lone Samurai. Another thing that supports the theory is when Hiro asked his father what he knew about killing and he replied more than you think and then proceeded to give a pretty nifty martial arts demonstration.
The question also made me wonder if the lone Samurai is the same Samurai that Hiro used to read about as a child. That could possibly mean that Hiro and his dad share the same ability, I don't think any of the other heroes have passed down the exact same ability but Hiro's dad mentioned something about waiting a long time for someone who was worthy of the challenge (I can't remember his exact words). At the time I assumed he meant another member of his family with a special ability but maybe he meant with the same ability.
Bookmarks