A wakizashi dated Shōhei 5 (1350), signed in full as Ōsumi no Gon no Suke Taira Sadatsugu of Bitchū Province and long held in the Naitō house of Nobeoka, fixes the Sadatsugu of this entry in time: not the early-Kamakura Ko-Aoe smith of the same name, but the Nanbokuchō continuation of the Aoe line in Bitchū. The published sources treat Sadatsugu as one of the representative houses of Aoe, the name carried in unbroken succession from the close of the Heian period down through the Nanbokuchō era. Within that long descent they recognize several distinct smiths working in different generations under the single name, a point the NBTHK states outright when it observes that within the Bitchū Aoe line 'multiple smiths of the same name are recognized'[[c:1]]. The most individual of the Nanbokuchō hands is Ōsumi no Gon no Suke Taira Sadatsugu, whose dated works run from Genkō through Shōhei and whom the published sources call a smith who 'reflects a notably strong individuality in his workmanship even within his school'[[c:2]].

His recognized work is the hira-zukuri tantō and wakizashi, wide in body and sun-nobi, thin in kasane with shallow sori, the bold and powerful shape of the Nanbokuchō peak. Over a ko-itame mixed with mokume whose grain stands finely into the so-called chirimen-hada, with minute ji-nie, chikei, and patches of clear sumi-hada-toned jifu, he takes the suguha broad, mixing in slight ko-chōji. The nioiguchi is tight and somewhat subdued, with thick ko-nie; ashi and yō enter densely, carrying the inward-slanting saka-ashi of the school. The most striking thing his judges name is what happens inside the temper. The nie gathers and condenses into shima-ba, islands of hardening within the ha; kinsuji and sunagashi are active; and the bōshi turns back in a ko-maru tempered deeply and long down the side. It is this that the published sources mean when they write that 'a certain bold, uninhibited flavour overflowing with vigour is why he is said to be an atypical presence within his school'[[c:3]].

The jigane is the constant beneath that activity. The forging is a tightly worked ko-itame with mokume, the grain standing finely to a crêpe-like chirimen texture, into which enter fine ji-nie in minute particles, delicate chikei, and the sumi-hada-toned mottling that the published sources call the clear-steel patches of Aoe; over it a faint, midare-leaning utsuri rises. The carving program on the tantō is devotional and economical, a bonji seed-syllable with a suken or gomabashi cut beneath it and run off; the long signature sits centrally in somewhat thick chisel, and the file marks are the steep ō-sujikai of Bitchū. These last two, the ō-sujikai tang and the ha-ura reverse-chisel manner of the inscription, are the tang tells the published sources set against the Bizen file when they place a blade with Aoe rather than its near neighbour.

The Sadatsugu name in the Nanbokuchō does not resolve to one man. A second body of signed work, dated through Jōji, Eiwa, and Kōryaku, is by a different and slightly later smith whom the published sources connect with the title Saiga Tarōbyōe no Jō, a maker known for cutting comparatively small signatures and favouring a calm, low-tempered straight hamon. His tantō and naginata-naoshi run a narrow hoso-suguha over a ko-itame that flows toward the edge, the nioiguchi tight with ko-nie, the edge breaking into hotsure, the bōshi a small maru or a yakizume finish. One such wakizashi the judges read as sharing a common thread with neighbouring Ko-Mihara in its standing nagare-itame and the hotsure of its fine suguha, yet on close view deeper and more active in the ha, and so affirmed as Aoe. The third face of the record is the ō-suriage mumei or gold-inlaid naginata-naoshi judged Sadatsugu, and the NBTHK explains the practice plainly: because Aoe Sadatsugu has been held first-rank since the Kanchiin-bon Meizukushi, with the Shinkan Hiden-shō valuing Bitchū work at the supreme grade, there is an old habit of attributing a typical, finely made unsigned Aoe blade to him. On the Ebi Kusari-giri naginata-naoshi they make it explicit, that such a gold-inlaid 'Sadatsugu' does not point to the Ko-Aoe smith himself but uses the name 'in the sense of a representative superior work of the school'[[c:4]].

What sets this Nanbokuchō Aoe apart is exactly what the published sources name as its own. Where the work resembles its neighbours it is by tradition rather than by borrowing: the standing itame with jifu and ji-nie is the Aoe jigane, and the temper, the judges write, follows 'what may be called the Aoe tradition, a suguha into which saka-ashi enter'[[c:5]]. On the ō-suriage attributions a bright midare-utsuri stands clear, and over it a suguha mixed with ko-chōji, ko-gunome, and small midare takes a saka-gakari turn, nioi-dominant and bright, kinsuji and sunagashi fine. The inward-slanting feet and clusters, the clear utsuri, and the bright tight nioiguchi are the marks that hold a blade to Bitchū and away from the Bizen chōji it might otherwise be mistaken for; against the famed Ko-Aoe name the surviving signed and attributed work is read.

For the collector Sadatsugu is a scarce Nanbokuchō name rather than a common one. Fujishiro grades him Jō saku. He has no National Treasures and no Important Cultural Properties; his record runs instead through one Tokubetsu Jūyō and fourteen Jūyō, with one prewar Jūyō Bijutsuhin, sixteen designated works in all on record. The published sources call the Shōhei 5 Ōsumi no Gon no Suke wakizashi a kessaku and the very finest among his works, sound in both ji and ha, and note that as surviving examples by this smith are few the dated pieces carry high documentary value. His blades descend through documented houses: the Tokubetsu Jūyō wakizashi in the Naitō family, lords of the Nobeoka domain in Hyūga; a dated wakizashi held by the Onuki family, hereditary chief retainers of the Satake lords of Akita; and two of the gold-inlaid naginata-naoshi, bearing the names Kitakaze and Ebi Kusari-giri, owned by Miura Shōgen, a senior retainer of the Kishū Tokugawa, one of them received from the prelate Tenkai. With only a small number in the Tokubetsu Jūyō and Jūyō tiers, a signed Aoe Sadatsugu comes to market only seldom, and a privately held example is a notable thing for a collector to encounter, a document of how the celebrated Aoe name was carried into the Nanbokuchō age.

A wakizashi dated Shōhei 5 (1350), signed in full as Ōsumi no Gon no Suke Taira Sadatsugu of Bitchū Province and long held in the Naitō house of Nobeoka, fixes the Sadatsugu of this entry in time: not the early-Kamakura Ko-Aoe smith of the same name, but the Nanbokuchō continuation of the Aoe line in Bitchū. The published sources treat Sadatsugu as one of the representative houses of Aoe, the name carried in unbroken succession from the close of the Heian period down through the Nanbokuchō era. Within that long descent they recognize several distinct smiths working in different generations under the single name, a point the NBTHK states outright when it observes that within the Bitchū Aoe line 'multiple smiths of the same name are recognized'[[c:1]]. The most individual of the Nanbokuchō hands is Ōsumi no Gon no Suke Taira Sadatsugu, whose dated works run from Genkō through Shōhei and whom the published sources call a smith who 'reflects a notably strong individuality in his workmanship even within his school'[[c:2]].

His recognized work is the hira-zukuri tantō and wakizashi, wide in body and sun-nobi, thin in kasane with shallow sori, the bold and powerful shape of the Nanbokuchō peak. Over a ko-itame mixed with mokume whose grain stands finely into the so-called chirimen-hada, with minute ji-nie, chikei, and patches of clear sumi-hada-toned jifu, he takes the suguha broad, mixing in slight ko-chōji. The nioiguchi is tight and somewhat subdued, with thick ko-nie; ashi and yō enter densely, carrying the inward-slanting saka-ashi of the school. The most striking thing his judges name is what happens inside the temper. The nie gathers and condenses into shima-ba, islands of hardening within the ha; kinsuji and sunagashi are active; and the bōshi turns back in a ko-maru tempered deeply and long down the side. It is this that the published sources mean when they write that 'a certain bold, uninhibited flavour overflowing with vigour is why he is said to be an atypical presence within his school'[[c:3]].

The jigane is the constant beneath that activity. The forging is a tightly worked ko-itame with mokume, the grain standing finely to a crêpe-like chirimen texture, into which enter fine ji-nie in minute particles, delicate chikei, and the sumi-hada-toned mottling that the published sources call the clear-steel patches of Aoe; over it a faint, midare-leaning utsuri rises. The carving program on the tantō is devotional and economical, a bonji seed-syllable with a suken or gomabashi cut beneath it and run off; the long signature sits centrally in somewhat thick chisel, and the file marks are the steep ō-sujikai of Bitchū. These last two, the ō-sujikai tang and the ha-ura reverse-chisel manner of the inscription, are the tang tells the published sources set against the Bizen file when they place a blade with Aoe rather than its near neighbour.

The Sadatsugu name in the Nanbokuchō does not resolve to one man. A second body of signed work, dated through Jōji, Eiwa, and Kōryaku, is by a different and slightly later smith whom the published sources connect with the title Saiga Tarōbyōe no Jō, a maker known for cutting comparatively small signatures and favouring a calm, low-tempered straight hamon. His tantō and naginata-naoshi run a narrow hoso-suguha over a ko-itame that flows toward the edge, the nioiguchi tight with ko-nie, the edge breaking into hotsure, the bōshi a small maru or a yakizume finish. One such wakizashi the judges read as sharing a common thread with neighbouring Ko-Mihara in its standing nagare-itame and the hotsure of its fine suguha, yet on close view deeper and more active in the ha, and so affirmed as Aoe. The third face of the record is the ō-suriage mumei or gold-inlaid naginata-naoshi judged Sadatsugu, and the NBTHK explains the practice plainly: because Aoe Sadatsugu has been held first-rank since the Kanchiin-bon Meizukushi, with the Shinkan Hiden-shō valuing Bitchū work at the supreme grade, there is an old habit of attributing a typical, finely made unsigned Aoe blade to him. On the Ebi Kusari-giri naginata-naoshi they make it explicit, that such a gold-inlaid 'Sadatsugu' does not point to the Ko-Aoe smith himself but uses the name 'in the sense of a representative superior work of the school'[[c:4]].

What sets this Nanbokuchō Aoe apart is exactly what the published sources name as its own. Where the work resembles its neighbours it is by tradition rather than by borrowing: the standing itame with jifu and ji-nie is the Aoe jigane, and the temper, the judges write, follows 'what may be called the Aoe tradition, a suguha into which saka-ashi enter'[[c:5]]. On the ō-suriage attributions a bright midare-utsuri stands clear, and over it a suguha mixed with ko-chōji, ko-gunome, and small midare takes a saka-gakari turn, nioi-dominant and bright, kinsuji and sunagashi fine. The inward-slanting feet and clusters, the clear utsuri, and the bright tight nioiguchi are the marks that hold a blade to Bitchū and away from the Bizen chōji it might otherwise be mistaken for; against the famed Ko-Aoe name the surviving signed and attributed work is read.

For the collector Sadatsugu is a scarce Nanbokuchō name rather than a common one. Fujishiro grades him Jō saku. He has no National Treasures and no Important Cultural Properties; his record runs instead through one Tokubetsu Jūyō and fourteen Jūyō, with one prewar Jūyō Bijutsuhin, sixteen designated works in all on record. The published sources call the Shōhei 5 Ōsumi no Gon no Suke wakizashi a kessaku and the very finest among his works, sound in both ji and ha, and note that as surviving examples by this smith are few the dated pieces carry high documentary value. His blades descend through documented houses: the Tokubetsu Jūyō wakizashi in the Naitō family, lords of the Nobeoka domain in Hyūga; a dated wakizashi held by the Onuki family, hereditary chief retainers of the Satake lords of Akita; and two of the gold-inlaid naginata-naoshi, bearing the names Kitakaze and Ebi Kusari-giri, owned by Miura Shōgen, a senior retainer of the Kishū Tokugawa, one of them received from the prelate Tenkai. With only a small number in the Tokubetsu Jūyō and Jūyō tiers, a signed Aoe Sadatsugu comes to market only seldom, and a privately held example is a notable thing for a collector to encounter, a document of how the celebrated Aoe name was carried into the Nanbokuchō age.