Oakland Bay, WA. The Genuine Kumamoto is a Purebred Pedigree Sikamea Species Oyster. Kumamoto are definitely a giant among oysters, but not because they are large. It is, in fact, quite small, only slightly larger than the tiny Olympia oyster. With its deep cupping and highly sculptured, fluted shell, this smooth, fruity morsel has a dedicated fan club. Lovers of Kumos will wait an eternity for them, and claim that with them they can love as long.