Assaku-ki, or automatic pressing machine.
Yabuta is a brand name of automatic sake press machine. However, like Kleenex or Q-tips, this one brand is often used as a generic term to refer to any make of an The purpose of this machine is to separate the alcohol from the unfermented rice solids that are left over in the sake mash. The leftover unfermented rice solids are known as Kasu, which is a by-product of pressing in this machine. Kasubuai is the ratio of left over kasu rice solids. If the Assaku-ki presses with great force, the kasubuai is low. If the Assaku-ki presses gently, the kasubuai is high. A higher kasubuai is generally desired for premium sake.