They are Japanese words alright, but the useage is relatively unnecessary.
Gaigatron- okimi is Metalhawk referring to Gigatron as Prince/emperor. It is a respectful term that wouldn't be used if they were on opposing sides. The equivalent would be Optimus referring to Megatron as Lord Megatron...
Kitakyushuu is referring to the south of the southern island of Japan.
Musashi is referring to (most likely) Miyamoto Musashi, a famous swordsman who supposedly mastered double sowrd weilding. Musashi has become such a legend now, his blade will often be used as a magical sword in many types of fiction. It was a very strong blade in Chrono Trigger for example.
I guess it's valid in its usega, well aside from Okimi. But Personally I hate it when people chuck in a 'san' or whatever just to make the point about them having japanese knowledge. If they are supposed to speaking Japanese, it probably would have worked better had they just done it all in english with the old "translated from Japanese" in the corner trick.