Types of Short Swords Explained in Detail: Differences Between Aikuchi, Yoroidoshi, Koshigatana, Kougai, and Kaiken
* Image is for illustrative purposes only.Table of Contents
What is Tanto (Short Sword) — Blade Length Standards and Definition
In the classification of Japanese swords, "tanto" (short sword) is a general term referring to bladed weapons with a blade length (hachou) of less than one shaku (approximately 30.3 cm). However, in reality, the term "tanto" is a collective designation for multiple forms and types, each with its own unique name and characteristics.
This article will provide a detailed explanation of each form encompassed under "tanto" from the perspectives of structure, usage, and historical context.
Aikuchi — The Representative Handguard-less Self-Defense Blade
Definition and Structure
Aikuchi is a representative form of short sword without a "tsuba" (handguard). The name "aikuchi" derives from the fact that the boundary between the blade and handle (tsuka) connects as if "the mouth is closed" without a tsuba. There is no tsuba at the junction of the blade and handle, and it has a streamlined appearance with the koiguchi and hand area in close contact.
Era and Usage
Aikuchi became particularly widespread during the Edo period as a self-defense tool for samurai women and upper-class townspeople. Due to the absence of a tsuba, its striking power is low, but it does not obstruct when carried in the bosom and allows for quick unsheathing. In the inner quarters (women's residential areas) of samurai residences, it was cherished as an essential self-defense implement.
Decorative Nature
In addition to their function as self-defense tools, many aikuchi possess high decorative qualities. Aikuchi decorated with techniques such as chinkin (gold inlay), makie (lacquer painting), and raden (mother-of-pearl inlay) were treasured as bridal furnishings and gift items. Masterworks with elaborate decorations are particularly highly valued in collections.
Yoroidoshi — Practical Weapons Designed to Target Gaps in Armor
Definition and Structure
Yoroidoshi is a short sword designed to be thrust through gaps in armor (kacchu). It is characterized by a cross-section shaped like a triangle or diamond close to a square, with a narrow blade width and high rigidity. Many examples also feature "moroba" (double-edged blades) with edges on both sides.
Technical Background
While ordinary swords are primarily designed for cutting with a thin, sharp blade, yoroidoshi is designed with thrusting as the highest priority. It is a blade specialized for an extremely practical battlefield purpose: being thrust through gaps in armor plating—under the arms, between the neck and helmet, through eye holes—to defeat the enemy.
Historical Background
Yoroidoshi was most needed during the Southern and Northern Courts to Sengoku periods (14th–16th centuries), when armor development peaked. In this era, when samurai faced battle wearing full armor such as domaru, oyoroi, and tosei-gusoku, there arose a demand for weapons capable of piercing armor. From the Edo period onward, as the wearing of armor became formalized, the practical need for yoroidoshi declined, though its value as a collectible remains high today.
Evaluation in the Modern Market
The sharp decline after the Edo period can be attributed directly to the formalization of armor-wearing practices and the loss of market value for a function specialized in thrusting during an era of peace. Due to the small number of surviving examples, yoroidoshi are valued highly for their rarity in the modern sword market, and particularly well-preserved specimens with clearly defined diamond-shaped cross-sections command particularly high prices.
Koshigatana — The Daily-Carry Blade of the Muromachi and Sengoku Periods
Definition and Usage
Koshigatana is a blade with a length between that of tanto and wakizashi (approximately one to one-and-a-half shaku), worn at the hip for daily use. In current classifications, it occupies a boundary between tanto and wakizashi.
Historical Position
During the Muromachi period, the practice of wearing "daisho"—a pair consisting of a tachi and katana together with a wakizashi—became widespread, but during the transitional period before this culture was fully established, koshigatana served as the daily carry blade of samurai. The name "koshigatana" itself reflects a functional designation meaning "a blade worn at the hip," and it represents a product of an era when function took priority over form.
Kogai — A Unique Implement as Both Martial Equipment and Practical Tool
Definition and Structure
Kogai is a slender metal rod shaped like a hair-styling tool (kogai), which is housed on the side of the sheath (saya) as a pair with a kozuka (small knife). Its function as a blade is supplementary; it primarily served as a multipurpose portable item used for grooming and as a practical tool.
Relationship to Swords
Kogai is not an independent "blade" but is housed in the sheath as an accessory to wakizashi or katana. However, because it is classified as sword furniture, in the context of sword collections it is often traded as a "complete set with kogai." The presence or absence of a kogai is an important evaluation point in assessing the completion of the koshirae (fittings).
Era and Decoration
Kogai underwent decorative development from the Azuchi-Momoyama through Edo periods. Kogai decorated with intricate metalwork by kanakoushi (metal artisans) are today highly valued as important artworks forming part of the sword's koshirae (fittings).
Kaiken — The Self-Defense Blade Carried by Women
Definition and Characteristics
Kaiken is a self-defense short sword that women carried concealed in their bosom, also called "fukorogatatana" (bosom blade). It is most often in the aikuchi (handguard-less) style and features an elegant exterior finished with shirasaya (plain wood scabbard) or decorated with makie and raden.
Wedding and Kaiken
In samurai society, kaiken was one of the bride's "marriage trousseau" (bridal furnishings). Kaiken used in wedding ceremonies such as the "sankon" (three cups ceremony) held symbolic meaning representing the bride's chastity and spirit. Even today, in traditional Shinto wedding ceremonies in Japan, brides dressed in shiromuku (pure white wedding kimono) carry kaiken, and this cultural tradition continues to this day.
As a Means of Self-Inflicted Harm
Beyond its role as a bridal accessory, kaiken also served as a means of committing "jigai" (self-inflicted death) should a samurai woman fall into enemy hands. Surviving examples of kaiken with particularly thin and short handles designed to prevent the hand from slipping when cutting the carotid artery demonstrate that practical self-defense design philosophy lay beneath their decorative exterior.
Size
The typical kaiken has a blade length of approximately 5 to 8 shaku (15 to 24 cm), making it relatively small among tanto. It is designed to fit compactly from handle to sheath as a single unit, characterized by its portability without adding bulk.
Gomabashi and Nakiri — Ceremonial and Practical Short Blades
These items rank lower as "blades," but they exemplify the broader scope of Japanese sword culture.
Gomabashi: A ceremonial short blade-shaped tool used in Buddhist gomma (fire ritual) ceremonies. It has little to no actual edge and carries religious meaning rather than practical cutting function. It is strongly characterized as Buddhist paraphernalia and positioned as a religious symbol borrowing the form of a blade.
Nakiri: A short blade-shaped cutting tool derived for culinary use. While not a "Japanese sword" in the strict sense, it represents an important example of how Japanese blacksmithing techniques were applied to household cutlery.
Comparison Table of Each Type
| Type | Tsuba | Primary Use | Primary Users | Peak Era |
|---|---|---|---|---|
| Aikuchi | None | Self-defense, gifts | Samurai women, upper-class townspeople | Edo period |
| Yoroidoshi | Present/None | Combat (thrusting) | Samurai (when wearing armor) | Southern and Northern Courts to Sengoku |
| Koshigatana | Present | Daily carry | Samurai generally | Muromachi to Sengoku |
| Kogai | — | Hair grooming, carry | Samurai, upper-class townspeople | Azuchi-Momoyama to Edo |
| Kaiken | None | Self-defense, weddings | Samurai women | Edo period to present |
How to Read Koshigatana and Its Differences from Wakizashi
Koshigatana is read as "koshigatana," not "yōtō." It is a designation frequently appearing in medieval texts that referred generally to practical small blades worn at the hip.
The difference between koshigatana and wakizashi is fundamentally a matter of "terminology differing by era." The daily-carry blades up until the Muromachi period were called koshigatana, with handguard-less aikuchi fittings being the mainstream. When the system of wearing two blades (daisho) was established in the Edo period, blades of one shaku or more but less than two shaku worn alongside the main sword came to be called "wakizashi," and tsuba-equipped fittings became standard. In other words, wakizashi is the formalized terminology of the early modern period, while koshigatana represents the medieval terminology from which it originated.
What Is Called the "Intermediate Between Sword and Short Sword" — Sunnobi Tanto and Ko-Wakizashi
When searching for "a blade of intermediate length between sword and short sword," the applicable options are the sunnobi tanto (oversized short sword) with a blade length around one shaku (approximately 30.3 cm), or the ko-wakizashi (small wakizashi) measuring slightly over one shaku. In legal terms, blades under one shaku are classified as tanto and those from one shaku to under two shaku as wakizashi, but morphologically they form a continuum, and many large short swords around one shaku in length were made during the Southern and Northern Courts period. Details on sunnobi tanto are explained in Guide to Sunnobi Tanto Types.
The Difference Between Aikuchi and Dos (Dagger)
"Dos" is a slang term originating from gamblers' and rough-types' argot, and typically refers to crudely made aikuchi-style short swords. While formally both are "handguard-less short swords," the artistic merit and craftsmanship of a properly constructed aikuchi tanto differ entirely from mass-produced, unmarked utilitarian short blades. Under current law, possession of short swords registered as art swords is lawful, but carrying unregistered blades is subject to restrictions under the Firearms and Swords Law and the Misdemeanor Punishment Law.
The Difference Between Kaiken and Fukorogatatana
Kaiken (懐剣) and fukorogatatana / kaitō (懐刀) both refer to self-defense short swords carried concealed in the bosom and are in substance essentially the same thing. "Kaiken" is used in ceremonial contexts such as wedding attire, while "kaitō" is also used metaphorically to refer to one's closest retainer, as in "the lord's trusted retainer." The tradition of samurai women being given kaiken with shirasaya or brocade wrapping as part of their marriage trousseau persists in contemporary Japanese traditional wedding ceremonies.
Conclusion — The Layered Japanese Culture Reflected in Tanto Diversity
Each form of tanto is a product of Japanese blade culture optimized for its respective era, social class, and purpose. Rather than defining it simply as "a blade with less than one shaku of length," understanding the historical context and function of each form brings the depth of Japanese swords into sharper focus.
For collectors and enthusiasts, understanding the characteristics of each form is the first step in broadening one's appreciation. Particularly aikuchi and kaiken possess high artistic merit, and many masterworks with elaborate fittings survive to the present day. TOKUENZA carefully curates each form of tanto and allows for detailed online viewing through photographs and comprehensive explanations.
