That’s because it is one of important elements to determine the scope of protection of a trademark.
However, do you always consider how average Japanese people would pronounce the trademark which you are filing?
Because it is possible that the pronunciation by Japanese customers is different from the intended one (“correct pronunciation”, in other words).
Scope of protection of a trademark in Japan shall be determined, taking such local pronunciation thereof in Japan into acount.
Accordingly, it is problem if the local pronunciation were different from your intended one.
Can you let me show an example?
Although the correct pronunciation of this mark is “he-i-nn-zu”, a average Japanese may pronounce it as “ha-ne-su” if the mark is not known very well in Japan.
It means that others have a chance to obtain a registration of another mark pronounced as “he-i-nn-zu” even if you own a registration of the mark “Hanes”.
In this case, you should file an application for the Katakana character mark pronounced as “he-i-nn-zu” as well as one for the mark “Hanes”.
That’s why, I think it is dangerous to file a trademark application in Japan without considering local pronunciation.