Ohishi Whisky is distilled entirely from rice and aged in either Brandy or Sherry Casks. In order to ensure the quality of the spirit, the Master Distiller utilizes 30% estate grown grain for distillation, with the remaining 70% of rice (Mochi) coming from the surrounding Kumamoto prefecture.

Weeds in the estate rice paddies are controlled by koi fish that swim about the grass and nibble the invasive plants. Varieties of estate-grown rice include Hino hikari, Mori no kuma-san, Yamada Nishiki, Gohyakumanishi (5 million stones) and Gin no Sato. Because of the rices efficient and subsequently clean fermentation, Ohishi uses a pot still made from stainless steel, as opposed to copper.