Three-Pronged Sword

The Sankozuka-ken: A Sacred Sword Where Shinto Meets Esoteric Buddhism

High in the mountains of Nikko, hidden away in the treasure hall of Futarasan Shrine, rests a small but extraordinary sword called the Sankozuka-ken (三鈷柄剣). Its name literally means "sword with a three-pronged-vajra hilt," and a single glance reveals why it has fascinated scholars and pilgrims for centuries. The slender blade was forged by Heian-period swordsmiths working in the Yamato tradition, while its hilt — cast in bronze in the unmistakable form of a Buddhist ritual implement — was added in the late Kamakura period. Together they form one of the most evocative surviving symbols of Japan's long history of spiritual fusion between Shinto and esoteric Buddhism.

Designated an Important Cultural Property of Japan in 1972, the Sankozuka-ken is housed at Nikko Futarasan Jinja, the great mountain shrine that, alongside Toshogu and Rinnoji Temple, makes up the UNESCO World Heritage site known as the Shrines and Temples of Nikko. For visitors curious about how Japan's two great religious traditions once breathed as one, this small sword is a quiet but powerful storyteller.

What Is a Sankozuka-ken?

To understand this sword, one must understand the sanko-vajra (三鈷杵, sankosho), a ritual implement central to Mikkyo, or Japanese esoteric Buddhism. The vajra originated in ancient India as a thunderbolt symbol, and Buddhism transformed it into a tool representing indestructible wisdom that cuts through delusion. The "three-pronged" version, with three points at each end, was carried by mountain ascetics and esoteric priests as a focus for meditation and ritual.

A Sankozuka-ken takes this ritual object and joins it to the body of a sword. The lower three prongs become the hand grip; the upper three prongs cradle the tang of the blade. The result is neither a pure weapon nor a pure ritual implement, but something in between — a consecrated sword used by Shugendo mountain practitioners in fire ceremonies such as the Saito-goma, a dramatic outdoor ritual still performed today. By striking the air with such a sword, the practitioner symbolically severs the bonds of worldly attachment and invokes the protective fire of the Buddhist deities.

Why It Was Designated an Important Cultural Property

The cultural value of the Sankozuka-ken at Futarasan Shrine lies in something deceptively simple: it has survived intact. According to surveys by Japan's Agency for Cultural Affairs, very few three-pronged-hilt swords from before the Muromachi period have come down to us in their original form. In most surviving examples, either the blade or the hilt was lost over the centuries and replaced with a later substitute. This piece is one of the rare survivors that preserves both the original blade and the original esoteric Buddhist hilt as a single, harmoniously matched whole.

The blade itself is a fine example of the Yamato tradition, the oldest of Japan's five great schools of swordsmithing, rooted in the temple workshops of the Nara region. Specialists note that its short tang, distinctive file marks, and straight-style hamon (temper line, hardened only along the upper portion of the blade) recall swords preserved in the eighth-century Shosoin treasure house at Todaiji Temple in Nara. This stylistic kinship pushes its production back to the Heian period, when ancient sword-making techniques were still alive in Yamato workshops.

The hilt, in contrast, was crafted in cast bronze during the late Kamakura period, when esoteric Buddhism flourished and the cult of mountain worship reached new heights. Its prongs are sharply flared and full of energy, marking it as a refined product of that age. The blade and hilt thus span more than two centuries of religious history, bound together as the prayers of generations of Nikko practitioners.

Highlights to Look For

What makes the Sankozuka-ken so memorable up close is the perfect proportional balance between its two halves. Although the blade is unusually slender and the hilt is small and flat, the strong outward thrust of the bronze prongs gives the whole piece a sense of poised tension. Visitors viewing it for the first time often comment on how compact it feels — a reminder that Shugendo practitioners needed an implement they could carry into the mountains, not a weapon for the battlefield.

Other features worth examining include:

• The double-shinogi blade form (両鎬造), in which both faces of the blade carry a ridge line — a relatively rare construction associated with ritual swords rather than ordinary tachi.
• The fine, drifting grain pattern in the steel (small itame flowing into masame), characteristic of the Yamato tradition.
• The "demon-eye" oval medallions running around the central grip, with eight-petal lotus motifs above and below — purely Buddhist iconography rendered in metal.
• The blurred misty quality of the temper line (匂口がうるむ), a subtle aesthetic feature treasured by sword connoisseurs as evidence of antiquity.

The sword is part of a far larger collection of donated weapons preserved by the shrine. Futarasan Jinja safeguards more than 170 swords, including two National Treasures and many Important Cultural Properties — a holding so significant that the treasure hall is sometimes called "the Shosoin of the Mountains."

Visiting the Treasure Hall

The Sankozuka-ken belongs to the broader collections of Nikko Futarasan Shrine and is exhibited from time to time at the Treasure Hall (Homotsukan) located at Chugushi, the middle shrine standing on the northern shore of beautiful Lake Chuzenji at the foot of Mount Nantai. Built in 1962 to house the shrine's vast collection of donated swords and the ritual artifacts excavated from the summit of Mount Nantai, the Treasure Hall is a destination in itself for lovers of Japanese arms, ritual art, and mountain religion.

Display rotations vary, so travelers hoping to see the Sankozuka-ken on a specific date are encouraged to check the shrine's website in advance. Even when this particular piece is not on view, the Treasure Hall almost always features the National Treasure great-sword inscribed Bishu Osafune Tomomitsu, the legendary giant sword Nenekirimaru (one of the largest Japanese swords in existence), and rotating selections of bronze ritual mirrors, vajras, and other relics that bring early mountain worship vividly to life.

Chugushi sits about 30 minutes by car from the Kiyotaki interchange of the Nikko-Utsunomiya Expressway, reached by climbing the famous switchbacks of the Iroha-zaka road. Visitors without a car can take a Tobu Bus bound for Yumoto Onsen from Tobu Nikko Station or JR Nikko Station and alight at the Futarasan Jinja Chuguushi-mae stop, roughly 50 minutes from the station.

Around Nikko

A visit to see the Sankozuka-ken pairs naturally with the wider wonders of Nikko. The Treasure Hall stands within walking distance of Lake Chuzenji, formed when Mount Nantai erupted in prehistoric times, and only a few minutes away from Kegon Falls, one of Japan's three great waterfalls and a powerful symbol of the spiritual landscape that drew ascetics here in the first place. From late April through mid-November, hardy pilgrims can also climb Mount Nantai itself; the trailhead lies just inside the Chugushi precinct, with registration at the shrine office.

Down the mountain in the main Nikko temple-shrine complex, often called Sannai, visitors will find the World Heritage cluster of Toshogu Shrine, Rinnoji Temple, and the original main shrine of Futarasan. The vermilion Shinkyo Bridge spanning the Daiya River is the historic gateway to this whole sacred precinct. Allowing two days for the area — one for Sannai, one for Chugushi and Lake Chuzenji — gives visitors time to experience both the lavish Edo-period architecture of Toshogu and the older, quieter mountain spirituality that the Sankozuka-ken so vividly embodies.