This is a beautiful Nambokucho blade attributed to the Nanbokucho period studenth of Chikuzen Samonji Sa Yukihiro. Yukihiro worked circa 1350 and was among the best of the immediate students of O-Sa. In addition to being a famous smith in his own right, Yukihiro went on to teach Hiroyuki and Sadayuki. The sword has a very long nagasa of 74.3cm and is very healthy and nearly ubu. The following are the bio on Yukihiro and his students as written by Markus Sesko.

YUKIHIRO (行弘), 1st gen., Kan´ō (観応, 1350-1352), Chikuzen – “Chikushū-jū Yukihiro” (筑州住行弘), student of Ō-Sa (左), there exists a tantō with the date signature of the first year of Kan´ō (1350) which is the oldest extant date signature of a Sa student, Yukihiro also displayed the closest workmanship to Ō-Sa, tantō measure like at Ō-Sa around 23 cm and are narrow whereas they tend somewhat to uchizori at Yukihiro, the mune is a mitsu-mune, the jigane is a ko-itame with chikei and much ji-nie, the hamon is a ko-notare mixed with gunome and ashi whereas the latter appear in a slanting manner along the fukura, also sunagashi and kinsuji appear, the bōshi is midare-komi, the yasurime are ō-sujikai, jō-saku ⦿

HIROYUKI (弘行), Shōhei (正平, 1346-1370), Chikuzen – “Hiroyuki” (弘行), Sa school (左), according to tradition the son of Sa Yukihiro (行弘), gunome with pointed yakigashira, jō-saku

SADAYUKI (定行), Shōhei (正平, 1346-1370), Chikuzen – “Chikushū-jū Sadayuki saku” (筑州住定行作), “Sadayuki saku” (定行作), Sa school, according to tradition a student of Ō-Sa (大左), other see him as student of Sa Yukihiro (左行弘), he moved later to Aki province and belonged there to the Sa-group that is referred to as Aki-Sa (安芸左) or Geishū-Sa (芸州左), there is a hira-zukuri tantō with the date signature of Shōhei twelve (1357) extant, itame-nagare mixed with masame, notare mixed with gunome in nie-deki, in addition hotsure and many hataraki within the ha, the bōshi has a pointed kaeri which starts his turn-back late, ryō-wazamono, jōjō-saku – It is said that a later Sadayuki moved to Hizen province where he joined the Hirado-Sa group (平戸左)