Kumamoto oyster Crassostrea sikamea is a common species found along the coasts of East Asia, it is a relatively slow-growing species with small but deeply cupped shells compared to other Crassostrea oysters. Its small size and unique shells may provide a good case for studying growth and shell regulation. C. sikamea prefers upper region of the intertidal zone and can tolerate harsh coastal environment relative to its sister species.Due to the lack of genomic resources, however, the genomic basis for its slow growth and environmental resilience has not been well studied.