Types and Classification of Mune (Back of the Blade)——What Iori-mune, Maru-mune, Kaku-mune, and Mitsu-mune Reveal About Schools and Eras
* Image is for illustrative purposes only.Table of Contents
What Is the Mune?——The Meaning of the Ridge on the Back of the Blade
When appreciating a nihontō, most people's eyes turn first to the hamon or the jigane. However, the mune——the ridge running along the back of the blade——is also an indispensable element for understanding the form of a sword. The mune refers to the ridge on the side opposite the cutting edge——the so-called "back" of the blade——and is classified into several types according to the cross-sectional shape of the blade.
While the shape of the mune does not produce as dramatic a visual effect as the hamon, it strongly reflects the technical traditions of sword schools and the aesthetic preferences of each era. A tōkō's choice of mune was not merely a matter of outward preference, but a decision deeply tied to the method of tanren, the method of yaki-ire, and the intended purpose of the sword. In sword kantei as well, the shape of the mune is regarded as one of the important clues for estimating a sword's attributed school and period of production.
The Four Basic Types of Mune——Iori-mune, Maru-mune, Kaku-mune, and Mitsu-mune
The shape of the mune is broadly classified into four types.
| Type | Alternate Name | Characteristics | Era / School |
|---|---|---|---|
| Iori-mune | The top of the cross-section forms a gently peaked mountain shape (reminiscent of the shape of a thatched hermitage roof), with the mune surfaces on both sides sloping evenly to form a ridge. It is the standard form used in shinogi-zukuri swords. The angle of the beveled mune surface differs subtly from tōkō to tōkō and can sometimes serve as a clue in kantei. It is noted that the mune side can smoothly deflect force when parrying a blow. | Adopted over a long period, from the kotō era through gendaitō | |
| Maru-mune | Kusa no mune | The top of the mune is rounded in a semicircular shape, and the cross-section draws a soft curve, giving a gentle impression to the eye. The mune body tends to be somewhat thick, and it can also be described as a form possessed of a uniquely soft quality. | Seen frequently on tachi of the Yamashiro-den (Rai School, Awataguchiha) from the Heian period through the Kamakura period, linked to an aesthetic sensibility unique to Yamashiro that favored rounded lines |
| Kaku-mune | Hira-mune | The top of the mune has a flat surface and the cross-section is close to a trapezoid. It is prone to the mistaken impression that it is common in the Sōshū-den, but it is properly understood as a vestige of the straight-bladed sword era. | The oldest mune form, seen most frequently on jōkotō (straight-bladed swords from before the Nara period). After the Heian period, when sori became standard, it was rarely adopted. |
| Mitsu-mune | Shin no mune | A special form in which multiple ridge lines run along the mune, with the cross-section forming a three-sided trapezoidal structure where the central face of the mune and its two flanking faces are clearly demarcated by ridges. It requires a high level of skill from the tōshō. Though frequently discussed in connection with the naginata, examples of its adoption on swords and tantō are the important kantei indicators. | A form seen frequently on swords and tantō of the Yamashiro-den and Sōshū-den |
The Relationship Between Mune Shape and School
The shape of the mune is closely linked to the characteristics of sword schools. As mentioned above, maru-mune was favored in the Yamashiro-den for a period, while in the Bizen-den (the sword-producing region centered on Okayama Prefecture) iori-mune was standard. The Bizen tōkō of schools such as the Ichimonji School and the Osafune School achieved a clean sword form through the use of iori-mune.
In the works of Masamune and Sadamune, representative tōkō of the Sōshū-den, the mune tends toward a relatively narrow and sharp iori-mune or a form close to kaku-mune. The technical characteristic of the Sōshū-den——the hamon with intense nie——also affects the mune side, and a phenomenon called mune-yaki, in which the hamon effect extends to the mune, can occur. The presence or absence of mune-yaki is also an important observation point in kantei.
In the Sanjō School and Awataguchiha of the Yamashiro-den (the sword-producing region centered on Kyoto), both iori-mune and maru-mune are used, but in either case the ridge line of the mune tends to be finished with exceptional delicacy and symmetry. The refined and sophisticated sword form unique to the Yamashiro-den is also expressed in the precise finish of the mune.
The Finishing of the Mune——Yasurime and Decoration
The surface of the mune is not only of a simple shape; it may be given a finishing treatment called kesho-yasurime. Kesho-yasurime is a technique of applying yasurime in a fixed pattern to the mune surface and various other parts of the blade, and it reflects the individuality of the tōkō and the fashions of the era.
Among the kesho-yasurime on the mune, there are diverse patterns, including the "kesho-giri" style in which a single horizontal line is filed in one by one, and styles in which yasurime are applied diagonally. These finishing patterns, alongside the tōkō's mei, serve as evidence of the "individual traits of the tōkō" and are referenced by researchers as grounds for estimating the attribution of mumei swords.
In addition, the treatment of rounding off the corner of the mune and the shape of the mune-machi (mune-machi: the part of the mune corresponding to the shinogi section) are also indicators of the care taken in finishing. On the works of master smiths, the line of the mune from the mune-machi to the kissaki is perfectly balanced like a single taut thread, and that gentle curve enhances the overall dignity of the sword.
Mune-yaki and the Structural Significance of the Mune
Mune-yaki is a phenomenon in which the yaki-ire intentionally or incidentally reaches the mune side. As exemplified by the hitatsura of the Sōshū-den, there was a bold yaki-ire technique in which the firing extended to the entire surface of the blade. Hitatsura is a technique perfected by the Sōshū-den tōkō in the Nanbokuchō period, producing a magnificent spectacle in which nie, ha, and tobi-yaki are scattered across the entire surface of the blade.
A sword with mune-yaki offers increased points of visual interest in appreciation, but the hardening of the mune side also presents the aspect of an increased risk of breakage or chipping. Tōkō who valued practical use chose designs that kept the mune side flexible, while tōkō who envisioned use for appreciation and ceremonial purposes pursued the visual richness of mune-yaki. Such differences in design philosophy were also reflected in the choice of mune shape.
The Practice of Appreciation——How to View the Mune
When actually holding and appreciating a nihontō (in the case of observing it drawn from its shirasaya under soft light), the following procedure is recommended for observing the mune.
- Tilt the blade and confirm the symmetry of the ridge line on the mune side. For iori-mune, check whether a symmetrical peak has formed on both sides; for maru-mune, check whether the curve is smooth; for kaku-mune, check whether the flat surface is cleanly rendered.
- Confirm that the curve of the entire mune line——from the nakago to the kissaki——is in harmony with the sori of the sword. The beauty of this line is an important element that determines "the quality of katanasugata."
When kantei certificates or exhibition descriptions note "mune——iori-mune" or "mune——maru-mune," this information functions as one piece of data in making a comprehensive judgment about the sword's place of origin, school, and era. By understanding just one mune shape, the tōkō's technical choices and the depth of tradition behind a sword become more concretely visible.
The appeal of the nihontō does not lie in the hamon alone. In the mune——the "back" of the sword——the aesthetic sensibility and technical philosophy of the tōkō are also inscribed. If you find a sword that interests you, please contact us through the inquiry form.
