Genkai Masakuni (Yoneo Muko: 1939 - 2025)
A Pioneer of Modern Mizu-Honyaki Craftsmanship
The name Genkai was inspired by the Genkai Sea, the waters surrounding the birthplace of master bladesmith Muko Yoneo in Saga Prefecture. He began his apprenticeship at the age of 15, and when he later became independent, his master bestowed upon him the name Masakuni. Throughout his life, he remained deeply connected to the traditions and spirit of his coastal hometown.
When Muko Yoneo began pursuing Mizu-Honyaki, Honyaki knives were far from common in the Japanese knife industry. At the time, many regarded the idea of hardening heated high-carbon steel by quenching it directly in water as impractical due to the extremely high failure rate. Cracking and warping during quenching were common, and few believed such knives could be produced consistently on a commercial scale.
Through years of relentless experimentation, patience, and extraordinary craftsmanship, Muko Yoneo refined this demanding process and became one of the craftsmen who helped establish Mizu-Honyaki as one of the highest expressions of Japanese knife making. Today, Mizu-Honyaki knives are admired worldwide for their exceptional cutting performance, remarkable hardness, and timeless beauty.
The manufacturing process closely resembles the traditional hardening techniques used in Japanese swordsmithing. Before quenching, a carefully prepared clay mixture is applied to the blade—a technique similar to the tsuchioki process used for Japanese swords. This clay controls the cooling rate during water quenching and creates the distinctive hamon (temper line), making every blade truly unique.
Depending on how the clay is applied, craftsmen can create a wide variety of hamon patterns, including graceful Notare (gentle waves), dramatic Sanbonsugi (three cedar trees), and even artistic designs inspired by Mount Fuji. These temper lines are not merely decorative—they are a visual expression of the bladesmith's skill and one of the defining characteristics of a true Honyaki knife.
Following the passing of Muko Yoneo in 2025, no successor has publicly continued his particular approach to Mizu-Honyaki craftsmanship. As a result, authentic knives bearing the Genkai Masakuni name have become increasingly scarce. Most examples available today are either blades forged during his lifetime or carefully preserved old stock that has only recently entered the market.
With each passing year, these knives continue to grow in rarity and are valued not only as exceptional culinary tools but also as significant works of Japanese craftsmanship.
Today, only a very small number of bladesmiths possess the knowledge, experience, and technical ability required to produce genuine Mizu-Honyaki knives.
Yoneo Muko (Genkai Masakuni), a legendary bladesmith deeply respected for his uncompromising craftsmanship and his mastery of Mizu-Honyaki, passed away on September 25th, 2025, at the age of 85. His passing marked the loss of one of the remarkable craftsmen of Japanese bladesmithing.
Since his passing, we have been fortunate to remain in close contact with the Muko family. Through their kindness, continued guidance, and conversations about Yoneo Muko and his work, we continue to deepen our understanding and appreciation of the craftsmanship, philosophy, and legacy he left behind. We are sincerely grateful to his family for continuing this relationship with us.
At YAMANI, we hold Yoneo Muko’s work and legacy in the highest respect. We sincerely hope that the extraordinary tradition of Mizu-Honyaki craftsmanship to which he devoted his life will continue to be preserved and passed on to future generations.
Beyond Our Current Collections
Our current collections showcases a range of knives available through YAMANI, while many additional knives and variations are also available.
If you are looking for something beyond what is currently displayed, please feel free to contact us. There are additional knives and variations available that are not currently shown in our current stock.
We can check availability to help you find the knife that best matches your needs.
Whether you are looking for a particular knife type, blade length, steel, finish, handle configuration, or a specific style of Japanese craftsmanship, tell us what you are looking for and we will do our best to find it for you.
Genkai Masakuni Knives Collections
See a sample of Genkai Masakuni knife restoration work.
Looking For a Genkai Masakuni Knife Not Listed Here? Please Contact Us.