[Nyororin]

I am personally a fan of the Concord wine from Nagano.

I would say that these days most of the wineries make an effort to use 100% Japanese grown grapes. It`s always a big selling point on the bottle. I know that there has also been a lot of pressure in recent years to stop using imports entirely, and to form a national regulation system. Right now it`s only regulated/monitored on the prefectural level. Nagano is one of the stricter ones - from what I understand wine fermented there has to be 100% Japanese grapes.