Senjūin

Senshi'in was a school of swordsmiths that arose in Yamato Province (present-day Nara Prefecture) and was active from the late Heian period through the Kamakura period into the Nanbokuchō period. Along with Tegaki, Taima, Shirihakae, and Hōshō, it is collectively called the "Yamato Goha" (Five Schools of Yamato), but is regarded as the oldest among them. The school's name derives from smithing conducted in the Senju Valley at the foot of Wakakusa Mountain in Nara, and is named after the Senju Hall (Senshi'in Hall) that was located there, which had Senju Kannon as its principal image. The Senju Hall was one of the temple buildings that traced its origins to Konshōji, the predecessor of Tōdaiji, and records of it appear in ancient texts from around the eighth century. The sword smiths of Yamato were groups that developed as subordinates to the great temples of Nanto, such as Kōfukuji and Tōdaiji, with the demand for weapons carried by their sōhei (warrior monks) as their background, and Senshi'in is likewise transmitted to have been a lineage of smiths patronized by Senshi'in, a subsidiary temple of Tōdaiji. The name Gyōshin is transmitted as the founder of the school, but there is no more certain evidence than that his period of activity was the late Heian period, and only the names of a few people, including Shigéhiro, are known from ancient times.

The working style demonstrates well the characteristics of Yamato tradition. The forging exhibits koshi-zori with firm bracing, featuring high shinogi and broad shinogi-width, forming the basic tachi-sugata. The jigane displays flowing itame with masame tendency, good jibaki, visible ji-kei, and a clear aesthetic quality. The hamon, based on suguha, incorporates ko-midaré and ko-gunome, with characteristic Yamato workings such as futae-ba, kuichigai, kinsuji, sunagashi, and yu-bashiri appearing abundantly. Its hallmark is classical and simple working, and it possesses the dignity of ancient tradition and antique craftsmanship because of being the oldest among the five schools—this is the most distinctive feature differentiating it from the other schools.

Because Senshi'in works show stylistic differences depending on the period, works from before the early Kamakura period are called "Kō-Senshi'in" (Old Senshi'in), and works from thereafter down through the Nanbokuchō period are simply called "Senshi'in" and are distinguished thereby. Kō-Senshi'in in particular displays ancient character, but extant transmitted works are extremely rare, and signed works with certain dating are scarcely seen. In fact, among extant works of the Senshi'in school, unsigned pieces constitute the majority, and their attribution relies on assessment of the working style itself rather than on signatures. The scarcity of works with certain signed attribution, and consequently the difficulty of tracing the accomplishments of individual smiths from their works, speaks to both the antiquity of this school and its character as a group of artisans attached to a temple.

In terms of evaluation, it is positioned among the finest works of koto (antique swords), and is highly regarded in sword history as the oldest source tradition among the Yamato Goha. One certain extant example is the "Tachi, Unsigned, Senshi'in" held by the Japanese Sword World Foundation, which is designated as a Tokubetsu Jūyō Tōken (Specially Important Sword). This work is known as a fine example demonstrating the ancient traditional working of the Senshi'in school, with forging displaying flowing itame with masame tendency and good jibaki, hamon showing suguha character with shallow undulation bearing kinsuji and sunagashi, and bright, vivid nioi-kuchi. The fact that, despite being unsigned, it is certainly attributed to Senshi'in on the basis of its working style clearly illustrates how this school is appreciated.