Koshirae Construction by Blade Type: Structural Differences and Material Selection for Uchigatana, Wakizashi, and Yari

What Is Koshirae—The True Nature of the Sword's "Garment"

The koshirae of a Japanese sword refers to the entire sword fitting system, including the saya that houses the blade, the tsuka that is gripped, the tsuba, and other elements. It is not merely a decorative element, but a functional system that determines the sword's portability, draw speed, and user safety.

Although the same term "koshirae" is used, the koshirae of the uchigatana, wakizashi, and yari differ fundamentally in their structure, materials, and manufacturing processes. Understanding these differences is essential both for sword collectors in selecting appropriate koshirae and for developing expertise in evaluating sword fittings.

Structural Comparison of Koshirae by Sword Type

Structure and Characteristics of Uchigatana Koshirae

The uchigatana is a sword with a blade 2 shaku (approximately 60 cm) or longer and was the most common sword type worn at the hip and carried daily by samurai during the Edo period. The defining characteristic of uchigatana koshirae is its design that accommodates the wearing style of "carrying the blade edge upward" at the hip.

Structure of the Saya (Scabbard)

The saya of the uchigatana is also called the "scabbard of the tachi koshirae" and is made to match the blade length. The basic material is magnolia wood (honoki), constructed as "two-piece assembly" by gluing two wooden boards together. The exterior is typically finished with lacquer—either "lacquered saya" (black lacquer, red lacquer, stone-pattern lacquer, etc.) or "fitted saya" (ray-skin or leather-wrapped).

At the tip of the saya is the ishizuki, fitted with a kojiri—a protective metal fitting that contacts the ground when the sword is worn at the hip. At the mouth of the saya is a koiguchi, a metal collar that both secures the sword when inserted and allows smooth drawing.

Handle Length Ratio

The traditional length ratio of the uchigatana handle is approximately 1/4 of the blade length. If the blade is 2 shaku 4 sun (approximately 72 cm), the handle would be approximately 6 sun (about 18 cm). This ratio is designed with the assumption of "gripping with both hands" and is optimized for efficiently executing sword techniques such as gedan and jodan.

Inside the handle is a "nakago hole" that houses the nakago of the blade, which is secured with a pin called a mekugi, made of bamboo or horn. The exterior of the handle is wrapped with ray skin, and over that is wrapped diamond-patterned silk thread or leather cord called the tsukamaki in a flat weave.

Selection Criteria for the Tsuba (Guard)

The tsuba of the uchigatana is selected according to the blade's thickness, curve, and the user's hand size. The shape varies—round, square, or aoi-shaped, among others—but the most critical factor is proper size alignment with the "kiriba" (thin metal washers sandwiched on both sides of the tsuba). The tsuba hole must correspond exactly with the cross-section of the blade's nakago, as even slight looseness poses a danger during sword use.

Additionally, in uchigatana koshirae, practical functions such as the "kojiri" and "saya-nari prevention" are emphasized. By including the "habaki" (a metal fitting placed at the base of the blade) inside the saya, noise is prevented and the edge is protected.

Structure and Characteristics of Wakizashi Koshirae

The wakizashi is a sword with a blade 1 shaku or longer but less than 2 shaku (approximately 30–60 cm), worn as a companion to the uchigatana in a matched pair. Although wakizashi koshirae share many elements with uchigatana koshirae, their differences in size and purpose give them unique characteristics.

Differences in Saya Shape

The wakizashi saya is shorter than the uchigatana saya, and the curve angle must strictly correspond to the blade's curve. Because the burden on the hip is lighter than with the uchigatana, an ornate "daimyo-style koshirae" developed. Often, decorative components such as inro and menuki are assembled lavishly, and koshirae of high artistic value in lacquer work and maki-e design exist.

Differences in Handle Length Ratio

The wakizashi handle typically has a ratio of "handle 0.3–0.4 to blade 1." Compared to the uchigatana, the handle ratio is often set slightly higher. This is a consideration for operability when using the wakizashi for "self-defense and close-range combat." Additionally, some wakizashi koshirae are designed with the premise of "single-handed use," in which case the handle thickness and wrapping method differ.

Storage of Kozuka and Koigai

Distinctive to wakizashi koshirae is the storage space for the "kozuka" and "koigai." Holes for the kozuka and koigai are typically set on the front and back of the saya, allowing for storage of the swordsman's daily items (small knife, hair ornament). This is a feature unique to wakizashi koshirae, not typically found in uchigatana koshirae, reflecting its function as a tool for the samurai's daily life.

Structure and Characteristics of Yari Koshirae

The yari koshirae differs significantly in structure from sword koshirae. While sword koshirae are designed for "drawing and use," yari koshirae are primarily designed for "protection of the point" and "safety during transport."

Hobukuro and Ishizuki

The core of yari koshirae is the "hobukuro"—a protective bag that houses the point portion. Made of leather or cloth with a core material inside, it protects the blade of the point from wear. The ishizuki (metal fitting at the end of the yari shaft) is designed to protect when thrust into the ground and to balance weight when the yari is held inverted.

Materials and Length of the Shaft

The spear shaft fundamentally differs from the sword handle, using a long wooden shaft of hard wood such as white oak or cherry called yagara. The length including the point is typically 1.5–4 m, with specifications varying by type—short-shaft yari, long-shaft yari, and large-body yari. The surface of the shaft is finished with "tōmaki" (spiral wrapping of rattan banding) or "kawamaki" (leather wrapping), which provide grip and durability.

Yarisaya and Transport Method

The "yarisaya," used to safely transport a yari during movement, is a cloth or leather cover that completely encloses the shaft. In modern decorative yari, the standard is storage in a set with the hobukuro and a wooden box.

Practical Points in Koshirae Selection Beyond Sword Type

The following are two key practical points to confirm when selecting koshirae:

• Habaki Fit Confirmation: The habaki is a metal ring fitted at the base of the blade (the boundary between the blade and the nakago), and the criterion is whether it is aligned with the koiguchi in a state that allows draw without play and smooth drawing. If the gap between the habaki and koiguchi is too large, the blade will move dangerously; if too small, the sword cannot be drawn.
• Matching the Curve to the Internal Saya Curve: If the blade's curve does not match the internal curve of the saya, the blade will interfere with the inner wall of the saya during drawing, causing wear and chips. When selecting koshirae, it is necessary to compare the measured values of the blade's curve angle (tip curve, mid-curve, root curve) with the saya curve.

Summary: The Essence of Koshirae by Sword Type Is the "Integration of Function and Beauty"

The koshirae of the uchigatana, wakizashi, and yari each have distinct structures optimized for their respective purpose, size, and transport method. When evaluating koshirae as a collector, cultivating genuine expertise requires attention not only to decorative beauty but also to functional quality indicators such as the following:

• Habaki alignment accuracy
• Koiguchi cutting shape
• Tsukamaki tightness

TOUKENZA's online catalog features numerous swords with koshirae, and through detailed product information explaining the condition of each component, customers can confirm the quality of the koshirae before purchase.