I am not so much interested in Japanese groceries (so far as I know, there are Japanese grocery shops in Syntagma area and Halandri in Athens), but I live much better with Chinese, Indian, and East Asian food stuff. In the city where I used to live in UK, there wasn't so much of a problem, as there were so many Chinese (from China and from elsewhere) and 'Asians' (English term for Indians, Pakistani and Bangladeshi), I could get almost anything I wanted.
Here in Piraeus, there are many foreigners, but not so many Chinese or 'Asians' as in the town I used to live and I needed to do some search, and the other day, I found a shop that seems to be able to supply some of the groceries I wanted.
There were not so many Japanese items, but to my surprise, I found this.
This shop has a bit of everything from every region of the world, and one of the featured areas was Middle and South America.
But I bought less exotic things (at least for me).
Prawn flavoured noodles, rice flour noodles, Chinese white tea and tom yam soup stock. I will try other stuff when Sarakosti finishes.