Kumamoto Oysters (Crassostrea sikamea) originated in Japan's Ariake Bay in the Saga Prefecture but pollution has made them nearly extinct in their area of origin. After World War II the Washington Department of Fisheries imported Japanese seed and planted it in Washington, Oregon and Hawaii. They are now found in Puget Sound's Oakland Bay, California's Humboldt Bay and Baja Mexico. I am eating the Oakland bay Kumamoto's. They are cultivated by the rack and bag method.
These are small - 2" - 3" in diameter with most in the 2" - 2 1/2" range and they are nearly round with deep ridged cups ranging from bone with green algae highlights to almost all algae green with some bone poking through. The caps are brown to dark green and almost black. The liquor has an almost neutral aroma with traces of sea weed while the meats smell like mild seaweed lightly seasoned with white pepper. It tastes fruity like lightly salted sweet melon joined by cucumber over a backdrop of umami. Brinyness is medium low, sweetness is medium plus, and minerality medium low. It has a clean, firm, crisp texture - no gristly membrane here. If you are new to oysters Kumamotos are a good place to start.
I am washing my Kumamoto's (aka Kumies) down with a bottle of Kevin Meinntsma's Sangiovese Carmenere Pyment (mead brewed with grape juice). Kevin is a much rewarded home brewer and his pyment is deep, complex with well-developed flavors and it marries perfectly with the Kumies. I can imagine drinking Kevin's pyment with a plate of melon, crackers, assorted fruit and some cheese and the Kumies have at about two thirds of the bases covered. The mild salt, the sweetness and the alcohol all work very well together. I rate the oysters 92.
You can buy Kumies from time to time on Amazon, although they run about twice what I get them for at Coastal Seafoods in Minneapolis.