From Google Maps
Rating: 3.5/5 (2 reviews)
Although not mentioned in tourist guidebooks, this cave was inhabited by those who came to the island while waiting for a reply from the shogunate (not mentioned in Japanese history). On the island, it's called Kamadoa (Commodore) Hall (the rank they held when they arrived in Japan). It's hidden by a fence to discreetly hide it from view. 5-7-2019: Cave entry challenge. Please forgive me for the photo caption below. I'd like to introduce another cave not mentioned in tourist guidebooks: Copper Cave. It's an atomic bomb storage facility that's not mentioned at all in Japanese-American history. I don't think you'll be able to go, so I'll post some photos.
It seems that it is not possible to visit the area as it is lined with private houses.