Page 6 is a bit of evidence that it is normal. Those are probably the leguminous nodules.

My first impulse when I read the title of this thread was to reply "No, it grows in other states, too", but if you're in Japan you probably won't get the reference to Tennessee football. (*grin*)

How will you be controlling the kudzu? It was so invasive in Virginia when I lived there a couple decades ago. It literally covers trees.

I wonder, is it toxic to small plant-eating animals like goats? If not, you could use them as a non-chemical way to control the plants, perhaps?