The Yamato (大和) school of sword making originated in the Yamato Province and gave rise to the five oldest sword forging technologies. These five schools of the Yamato tradition consist of the Senjûin (千手院), Hosho (保昌), Taima (当麻), Tegai (手掻), and Shikkake (尻懸). The Senjûin school (千手院) is acknowledged as the earliest and most elegant of the five schools. The Senjûin school belonged to a sub-temple of the Tôdaiji Temple located near to the Senjû valley on the eastern foot of the Wakakusayama (若草山) in Nara. During the Tenroku Era (天緑 970-973) the Senjûin (千手院) school moved from Senjû valley near Wakakusayama (若草山) to a location northwest of the Tôdaiji Sangatsu-dô. It is said that in the reign of Horikawa Tennô (1086-1107) a smith named Yukinobu (行信) made a naginata there for the first time. There is some controversy as to these dates and the current thought is that he actually worked around the Ninpei Era (仁平) (1151-1154). After that, this trade of smithing was handed down for a number of generations and they were called the Senjuin kaji (千手院鍛冶). There were number of smiths in this group, but zaimei swords by them are almost non-existent.
Swordsmiths belonging to this school were connected to the Senjûin Temple of Nara. The workmanship in this school was not particularly uniform. The school is divided into three sub-schools. Those smiths working from the late Heian Era through the early Kamakura Era are known as Ko-Senjûin (古千手院) smiths. Those working from the middle of the Kamakura Era through the Nanbokuchô Era are called the Chu-Senjûin (中千手院) (middle Senjuin) smiths. Sue-Senjûin (末千手院) (late Senjûin) refers to the swordsmiths of this school who were active in the Muromachi period after the Ôei Era.
It is believed that Yukinobu (行信) was the founder of the Ko-Senjûin school (古千手院). He is said to have been active around the Ninpei Era (仁平) (1151-1154). He was followed by Shigehiro (重弘). Shigehiro (重弘) served the Emperor, Gotoba, and is said to have later migrated to Akasaka (赤坂) in Mino (美濃) and founded the Akasaka Senjûin (赤坂千手院) school. Other smiths of the Ko-Senjûin (古千手院) school were Shigenaga (重永), Yukiyoshi (行吉), Yukimasa (行正), and Rikinao (力直). Signed examples from the smiths of this school are rare.
The characteristics of the Ko-Senjûin (古千手院) school are as follows:
SUGATA: Slender, tapering (funbari), with a ko-kissaki showing the elements of a classic tachi-sugata.
JIGANE: The jigane is well forged and beautiful. The mokume-hada is mixed with ji-nie and chikei. Yubashiri appears.
HAMON: The hamon is suguha hotsure, mixed with ko-choji and ko-midare. The nie are highly reflective and rather rough. Activity such as uchinoke, kuichigaiba, kinsuji, and inazuma are attractive and readily visible. The nijuba looks like yubashiri.
BÔSHI: The bôshi is yakitsume, nie kuzure, and kaen. The nie is highly reflective and tends to become rough from the yokote toward the tip.
Workmanship of the Chu-Senjûin (中千手院) school is generally similar to that of the Ko-Senjûin (古千手院) school, but it is somewhat inferior in grace and quality. The sugata is stout and shows features typical of this period.
When they made tanto they usually had the following characteristics:
SUGATA: Josun takenoko sori or Shobu-zukuri.
HAMON: Hoso suguha with much ko-nie.
BÔSHI: Most will be found in ko-maru shape with fine nie.
JITETSU: Very finely forged steel resulting in ko-mokume hada.
There are some surviving examples with signatures and dates of manufacture such as a tanto by Senjuin Yoshihiro (千手院義弘) that is dated Bunna ni-nen, hachi gatsu (文和二年八月日) or August of 1353. Other Chu-Senjûin smiths were Sadashige (定重), Rikio (力王), Kuniyoshi (国吉), Yoshihiro (義弘), and Kiyomune (清宗).
Swordsmiths we refer to as being of the Sue-Senjûin school produced swords that no longer have any traces of the Senjuin characteristics produced by the Ko-Senjuin and Chu-Senjuin smiths. They may be mistaken for poor Mino or poor Bizen works. The hamon is made in notare-midare without nie for the most part. The bôshi is in notare, midare, or yaki-kuzure. The jitetsu will seem hard with a mokume-hada.
A branch of the Senjûin (千手院) school was founded by Ryûmon Nobuyoshi (龍門延吉) who worked at the end of the Kamakura period around the Shôô period (正応-1288-1293), in the Ryûmon (龍門) area of the same name between the northern foot of the Yoshino mountain range and the village of Uda (宇陀). Nobuyoshi (延吉) made Yamato like blades with unobtrusive sugata, but he applied a different deki with utsuri and a quiet midare-ba with mixed-in ko-chôji which reminds us of the Bizen tradition. There are only a very few blades extant bearing the signature of Ryûmon Nobuyoshi, and many mumei works by him have the attribution to just the Senjûin school.
Tanobe Sensei stated, “When we see a blade with the typical Yamato-sugata whose classical jiba dates not later than the Kamakura period, and whose workmanship shows characteristics which cannot be classified into one of the four schools of, Taima, Tegai, Shikkake, or Hoshô, it is very likely that it is a Senjûin work.