Tsuru bishio is the flagship series of soy sauce for Yamaroku Shoyu and is aged the longest between 3-5 years. Tsuru(鶴) means "crane" and bishio (醤) means "condiment". In Japan, cranes are regarded as auspicious birds and symbolize longevity. It is said the song of cranes can reach the heavens, and Yamaroku Shoyu wants this soy sauce to be like the cranes which can reach the heavens and be known to everyone. Tsuru bishio is characterized as having a rich mellow flavor and is recommended for use in sushi, sashimi, tofu, grilled fish and as a secret ingredient for original dishes. A unique use of Tusuru bishio is putting it on top of vanilla ice cream which creates a very caramel like flavor. Adds a surprise twist for guests and customers at a restaurant.
Kioke (木桶) is a traditional Japanese wooden container used to ferment Japanese-style food. A microbe for fermentation settles in the kioke which turns it into the best brewing container.
The basic seasonings for a Japanese meal consist of the following: soy sauce, vinegar, mirin (sweet rice wine), and sake. All of these ingredients were brewed in a kioke back in Japan's Edo period during the years of 1603-1868. The fermentation of a microbe is required for making all the seasonings have the highest quality of taste. These were only possible through the use of the kioke which was hailed as the best container for brewing the seasonings.
The soy sauce industry today is more reliant on industrial production of the sauce, and now less than 1% of soy sauce production is brewed the traditional way using kioke. This method for creating authentic Japanese cuisine is slowly fading away due to the shift of mass manufacturing.
In Japan, only 1 company remains that produces the kioke barrels. With only about 60 kioke in their possession, most which will be impossible to use in 50 years, the current 5th generation owner of Yamaroku Shoyu took action and became a disciple from that company to learn how to build a kioke. This will help keep the traditional way of making soy sauces alive and will be passed on to the next generation.