Atrisian would not be japanese just as basic is not english. Basic is the common tongue of the galaxy. Now we can make the presupposition that basic is English because that is the language the films, however, it is faulty to assume they are the same language. We could also compare them on the merit that both are basically the trade languages of their worlds but once again, not the same language.
Think of it this way. You're reading a book set in japan written by an english author. Now the entire book is in english. All the characters when we see them speak have it written out in english. However, the characters are obviously speaking in japanese due to the fact that they are in japan, are japanese, and doing everything in japan. Unless specifically told otherwise, that is the obvious assumption to make. The same holds for galactic basic. It is its own language in its own universe. We just only know it as English.
Therefore, no, you could not say that japanese is analogous with Atrisian. Now, if for whatever reason, for RPing purposes you wanted to represent it that way. That would be your prerogative, however, they're not the same language in universe.
