2 kilograms This is a revised Nakura stone, a phantom natural whetstone. * Origin: Yamagata Prefecture * Use: This whetstone is often used in the preliminary sharpening process for Japanese sword polishing (between the medium and finishing whetstones). Specifically, it removes the scratches left by Bisuito (Iyo stone) and prepares the surface for the next Nakura stone process. * Characteristics: Because of its effectiveness (abrasive power), care must be taken to avoid excessive wear. * Current Status: It is now depleted and no longer mined. Therefore, it is extremely difficult to obtain and is treated as a "phantom whetstone" with high rarity value.