Unokubi-Zukuri, which literally translates to "cormorant's neck shape," is a unique style of Japanese sword that bears a distinctive silhouette reminiscent of the bird's neck. It owes its name to the distinct scoop in the back of the cormorant's neck, which it mimics with a similar dip in the distal third of the sword's spine. This dip then thickens back out at the Kisaki, the pointed tip of the sword, creating a design that is as striking as it is distinctive.

The main advantage of this design is weight reduction, makes it easier to handle (although the weight distribution is kinda different from traditional katana). Our Unokubi Zukuri katana are extra sharp so cutting with them is a lot of fun. 

Historically, the Unokubi-Zukuri style was practically absent in katanas until the 16th century. Its origin can be traced back to another weapon: the Naginata. This pole weapon, common from the 1100s to the 1400s, featured a curved cutting blade at the top and was often made in the Unokubi-Zukuri style. This was done to reduce weight and bring the weight balance closer to the hands, making it more maneuverable. This design, while reducing cutting ability, was not a significant drawback due to the leverage provided by the long pole of the Naginata.

However, as the katana grew in popularity in the 1400s, the Naginata fell out of favor. Many Naginata were reshaped into katana or wakizashi, a process that involved trimming the tang to shorten it and reshaping the tip. This process inadvertently created the Unokubi-Zukuri style in the newly fashioned swords, now referred to as "Naginata-Naoshi" style swords, meaning "repaired or reshaped Naginata".

In the mid to late 1500s, these Naginata-Naoshi style swords became popular, and swordsmiths began creating katanas in the Unokubi-Zukuri style, not as a result of reshaping Naginata, but as an aesthetic choice. The style was considered aesthetically pleasing, leading to its adoption in katana creation. This trend even spread to Korea, influencing the creation of some famous Korean swords, such as Admiral Yi Sun-shin's twin swords.

The Unokubi-Zukuri style can be easily confused with the Kisaki Moro Hazukuri katana, which is double-edged at the distal third, a design similar to Unokubi-Zukuri. These swords are often referred to as Kogarasumaru style swords, named after a famous sword that was a family treasure of the Taira family since the 12th century and made in this style. However, the primary difference lies in the functionality of these two styles. While both reduce weight, the Kisaki Moro Hazukuri style adds a sharp edge, compensating for the weak spot created by the reduction of material.