A wakizashi dated the eighth month of Ōei 20 (1413), handed down in the Ōshimazu family of Satsuma and raised to Tokubetsu Juyo at the twenty-sixth session, is signed in two lines Minamoto Saemon-no-jō Nobukuni, and within the character kuni the interior is cut as the character for "left." That reversed form is the first point the published sources give for this hand. The NBTHK opens its account with the house: 「信国は京鍛冶の名門で, 南北朝時代から室町時代にかけて大いに栄えた」 (Nobukuni was a distinguished Kyoto house of smiths that flourished greatly from the Nanbokucho into the Muromachi period). In the Muromachi branch Saemon-no-jō Nobukuni and Shikibu-no-jō Nobukuni are the representative smiths, and because both cut Ōei dates they are admired together as the Ōei Nobukuni. The line descends from Ryōkai and so from the Rai, and its first generation is said to have studied under Sōshū Sadamune; his works of Enbun and Jōji are the oldest dated pieces, and the Ōei smiths are reckoned the third generation. Tradition makes Saemon-no-jō the elder brother, but the published sources observe that among known dates the Nobukuni signature of Shikibu-no-jō is in fact the older, and they leave the relationship of the two to future research.
His most constant feature is carving. The published sources state that Saemon-no-jō and Shikibu-no-jō alike 「濃厚な彫物を得意としている」 (excel at dense carving), and the record bears it out. Flaming bonji, a kurikara in relief within a hitsu or pierced through it, sanko-ken and suken, hata-hoko, lotus pedestals and the invocation Hachiman Daibosatsu cut into the groove recur on both faces, often layered one over another. Of one Juyo wakizashi the judges write that the ji and ha are ordinary but the pierced kurikara in its hitsu is splendid. The temper he made his own is the second mark. Every generation of Nobukuni, the published record explains, worked chiefly in two manners, a suguha showing the Kyoto tradition and a notare inherited from Sadamune, and from the late Nanbokucho generation into the Ōei smiths 「互の目主調の乱れ刃の作域を新たに見ることが出来る」 (a working range of midare-ba led by gunome can newly be seen). Its idiom is a gunome that runs in pairs. The sources describe 「互の目が二つずつ矢筈形に連れた特色ある刃文」 (a distinctive hamon in which the gunome run two by two in the shape of an arrow-nock), mixed with angular and pointed teeth, ko-notare and choji-like elements. Ashi and yo enter, the ko-nie lies thick, kinsuji and sunagashi run through the ha, and tobiyaki and yubashiri gather over the crests under a bright nioiguchi.
Beneath both tempers lies one jigane. It is an itame mixed with mokume, flowing in places into masame toward the edge and tending to stand, with thick ji-nie and frequent chikei; where the forging tightens it becomes a ko-itame. The suguha that keeps the Kyoto tradition is the rarer face of his work. It runs narrow to medium, at times with a little ko-gunome, ko-ashi and yo entering, ko-nie well adhered and the habuchi fraying in places with kinsuji and sunagashi; the boshi runs straight to a ko-maru with hakikake. On the Ōshimazu wakizashi the judges call that suguha 「匂口明るく刃中よく働き」 (bright in the nioiguchi and full of activity within the ha). Of an Ōei tanto in hoso-suguha they draw a comparison: 「応永備前も直刃の作を好んで焼くがやはり信国の方が沸が強いようである」 (Ōei Bizen too likes to temper suguha, yet Nobukuni seems the stronger in nie). Another judgment holds that 「この時代の信国には直刃の出来は珍しく」 (suguha work is rare among Nobukuni of this period), and a large wakizashi tempered in suguha with a tight nioiguchi is said to recall Rai work.
Most of the record is wakizashi and tanto, hira-zukuri with mitsu-mune and somewhat extended in length, a build one judgment likens to Ōei Bizen. Signed tachi are few. A tachi dated Ōei 2 (1395) and a shobu-zukuri wakizashi dated Ōei 4 are assigned to the Nobukuni who worked from the close of the previous age into early Ōei, and their dates are called valuable material for the study of the school. Further dated pieces of Ōei 15, 20, 21, 30 and 34 follow. On the Ōei 34 tachi, a prewar Juyo Bijutsuhin, the published record notes 「丁子乱のにぎやかな刃文」 (a lively choji-midare hamon), unlike the Nanbokucho Nobukuni. A Shikibu-no-jō tanto in hitatsura is called a temper rarely seen in his work, perhaps made with the senior Kyoto school of Hasebe in mind. The signature completes the reading. The name carries the family Minamoto, so the smith commonly called Genzaemon-no-jō is properly Minamoto Saemon-no-jō, and his kuni is known by its reversed interior, a form the sources trace from Shitoku and Meitoku and find common in Ōei. Honma's inventory of the Imperial collection adds a caution, that this form 「必ずしも源左衛門尉に限ったことではなく, 後代信国にも見るところである」 (is by no means confined to Minamoto Saemon-no-jō but is also seen in later Nobukuni), so the workmanship must be weighed together with the mei. One tanto with the reversed kuni is accordingly left undecided.
The first Nobukuni, the published sources write, was a pupil of Sadamune whose work 「殆んど師貞宗に迫る作風を示している」 (shows a style that comes close to that of his master Sadamune). The Ōei generation carries that Sōshū nie into its paired gunome while keeping the bright Kyoto suguha, and his own combination is what sets him apart: the gunome running in pairs, the standing itame that flows toward the edge, the strong nie, and the layered devotional carving. The sources also record that other smiths cut a two-character Nobukuni mei in the same years, so that several namesakes are thought to have worked side by side, and unsigned or plainly signed pieces are referred to Saemon-no-jō or Shikibu-no-jō by the cut of the mei and the manner. The line later spread, one branch moving to Bungo in Kyushu and signing Nobukuni with a further name. Honma also notes that the Nobukuni nakago ends in a round kurijiri from the first generation to the last, unlike the ken-shaped tang of Sadamune.
Fujishiro grades the Ōei Nobukuni Jo-jo saku, and forty-four designated works stand on record. There are no National Treasures. One Important Cultural Property, a wakizashi signed as a dedication to the Fuji Hongū Sengen shrine by Minamoto Shikibu-no-jō Nobukuni and dated Ōei 24 (1417), is kept at that shrine. One blade holds Tokubetsu Juyo rank and thirty-nine more the Juyo, forty in the two tiers together; the Ōei 34 tachi is a prewar Juyo Bijutsuhin once held by Tokugawa Munetaka; and two blades, a ken and a tanto, are recorded in Honma's inventory of the Imperial collection. Forty-three of the designated works are signed and only one is unsigned. Recorded provenance runs through the Ōshimazu of Satsuma, the Tokugawa shogunal house and the Owari Tokugawa, Hosokawa Tadaoki and the Kuninomiya family. A tanto of the Kenshō-in at Tōnomine was presented by that temple to the shogunate at the succession from Ietsuna to Tsunayoshi, Tōnomine offering one sword from its treasury at each change of shogun. Of recorded whereabouts, examples rest at Atsuta Jingu and Ise Jingu, the Tokugawa Art Museum, the Sano Art Museum, the Kurokawa Research Institute and the Kyushu and Kyoto National Museums. For the collector the Ōei Nobukuni is a name within reach of patience: signed wakizashi and tanto of the Juyo tier come to market from time to time, while a signed tachi, which the published sources call 「頗る貴珍」 (exceedingly rare and precious), appears only rarely and is an occasion when it does.
