Countless time we have had dinner in local restaurant, where we had no idea what it was called.
The same was the case with our Naoshima restaurant. Apparently we arrived to Naoshima approx 1 week before the high season started, and it mend that most restaurants was either only open for lunch or closed all together.
From the harbour we went a little to the left and down the “large” street 100 meter where we found this little local place. Of course we sat on the floor (as with most places), and had fresh sashimi and rice. For four people we only paid less than 30 euros for our meal and drinks.