The localization is the same as far as I can tell, but a few typos and the like have been fixed.
The font is also improved:
I'm not sure if the bugs in the game have been ironed out. I've been meaning to replay it, so I suppose I'll give it a runthrough.
For anyone curious this is actually the second game in a series, the first being "Kenshuii Tendo Dokuta." I suppose you could give it a look if you're fluent in Japanese but it's fairly rough around the edges.
EDIT: I managed to load up my US save in this, and it's entirely the same except for the aforementioned typo fixes and font changes. As far as I can tell the occasional bug is still there. DS must be set to a certain language to play that language.