Today, I found that Grocery Court Cerfeuil at B1 in Gyre in Omotesando had a sign with the Discover Card logo. This particular sign had the JCB logo more prominently displayed than all the other logos, which made me believe that the merchant has their terminal from JCB.

However, I could not test its acceptance, since I did not bring my card on this trip because of the 2% foreign transaction fee.