it don't think it says when he dies, but in the movie, Hachi waits for his owner for 10 years, in real life though, only 9. sorry if it didn't help! i love that movie, every time i watch it, it makes me cry!! :"( :D
It is not clear at which age Parker who was Hachi's died but the cause was a fatal heart attack while in the lecture room. However, after nine years, the Parker and Hachi get reunited and head together into heaven. Check out http://en.wikipedia.org/wiki/Hachi:_A_Dog%27s_Story for more information.