Nagashige worked at Osafune in the opening years of the Nanbokuchō period, in the line that the published sources rank beside Kanemitsu as a 'standard-bearer of Sōden-Bizen'[[c:1]], the Bizen wing that took up Sōshū technique. His relationship to Chōgi was long misread, and the correction is one of the firmer facts on record: an older account made him Chōgi's younger brother, but his surviving signed blades carry dates of Kenmu 1 and 2 (1334–1335) and Kōei 1 (1342), while no work of Chōgi can be traced earlier than Shōhei 15, so the prevailing view today makes him Chōgi's elder brother. The dated anchor of that argument is concrete: a tantō signed Bishū Osafune-jū Nagashige and dated to the cyclical year kinoe-inu, Kenmu 1, once the sashiryō of Hon'ami Kōtoku, is his National Treasure.

His characteristic hand is the Sōden-Bizen midare, and it is most fully seen on the broad mumei katana that make up the bulk of his record. Over a standing itame mixed with mokume and nagare-hada, the jigane standing a little, he tempers a shallow notare or gunome base into which enter ko-gunome, ko-chōji and pointed togariba, with abundant ashi and yō. The nioiguchi is deep and bright, ko-nie adheres well with passages of rougher nie, and kinsuji and sunagashi run freely, small tobiyaki and yubashiri scattered along the edge. The bōshi runs midare-komi, rising to a pointed tip with hakikake or turning back in a small ko-maru. The construction is the full Nanbokuchō build, wide in mihaba with little width-taper, thick in kasane, an extended chū-kissaki or an ō-kissaki, hand-heavy and imposing.

The jigane carries the Bizen credential that keeps the work from turning purely Sōshū. Itame with thick ji-nie and well-entering chikei appears on every blade, and over it stands a midare-utsuri, clear where the forging is itame with mokume and falling to a faint utsuri-like cast on the rest. On the signed register, by contrast, the hand is tighter and calmer. The dated tachi run to a well-packed itame with fine ji-nie and only a light utsuri, the temper a chū-suguha or suguha-toned line mixed with ko-gunome and ko-chōji, even saka-ashi entering, ko-nie and ko-ashi present. Devotional carving, bonji set at the koshimoto, appears on more than one piece.

The published sources draw two further registers within his own work. On the signed tantō they read a more emphatic Sōshū cast than Chōgi himself, noting that 'among the signed survivors the tantō press the Sōshū manner further than Chōgi'[[c:2]]; these are hira-zukuri with a standing hada, a small notare with gunome growing vigorous toward the tip, sunagashi frequent and the pointed bōshi powerful. One signed tantō stands apart from everything else, its temper centered on kataochi-gunome mixed with squared kaku-gunome, evoking Kanemitsu, his circle and even Motoshige rather than the Chōgi midare; the sources call it 'a stylistic range unusual for Nagashige'[[c:3]] and value it as documentary material for the breadth of his manner.

What separates Nagashige from Chōgi is named the same way in entry after entry, and it is the whole of his kantei. His midare is of smaller scale and his yaki somewhat lower, yet 'the nie in both ji and ha surpasses Chōgi's'[[c:4]]; it is on this single recurring point that a Sōden-Bizen blade is converted into a Nagashige attribution. His distinction is carried by his own traits, the smaller, lower midare laid over a ji and ha more richly charged with nie, rather than by any feature borrowed from his brother. Traditionally his son Nagamori carries the line forward in a conspicuously chōji-based but somewhat lesser hand.

Fujishiro grades him Jō-jō saku. Signed, ubu Nagashige are extremely rare, and the body of his record runs through the Tokubetsu Jūyō and Jūyō tiers and the prewar Jūyō Bijutsuhin, above which stands his single National Treasure, the Kenmu 1 tantō held in the Hon'ami family. Several blades carry daimyō provenance: a katana given by Tokugawa Ieyasu to the Naruse house of Inuyama in Owari and long kept there, others through the Maeda of Kaga, the Nabeshima of Saga and the Shimazu. With only thirteen blades in the Tokubetsu Jūyō and Jūyō tiers and almost all of them held rather than traded, a signed Nagashige comes to light only seldom; a privately held example, where the broad Sōden-Bizen katana shows its smaller midare over an unusually nie-laden ji and ha, is a notable thing for a collector to encounter, and a document of how Bizen absorbed the Sōshū manner.

Nagashige worked at Osafune in the opening years of the Nanbokuchō period, in the line that the published sources rank beside Kanemitsu as a 'standard-bearer of Sōden-Bizen'[[c:1]], the Bizen wing that took up Sōshū technique. His relationship to Chōgi was long misread, and the correction is one of the firmer facts on record: an older account made him Chōgi's younger brother, but his surviving signed blades carry dates of Kenmu 1 and 2 (1334–1335) and Kōei 1 (1342), while no work of Chōgi can be traced earlier than Shōhei 15, so the prevailing view today makes him Chōgi's elder brother. The dated anchor of that argument is concrete: a tantō signed Bishū Osafune-jū Nagashige and dated to the cyclical year kinoe-inu, Kenmu 1, once the sashiryō of Hon'ami Kōtoku, is his National Treasure.

His characteristic hand is the Sōden-Bizen midare, and it is most fully seen on the broad mumei katana that make up the bulk of his record. Over a standing itame mixed with mokume and nagare-hada, the jigane standing a little, he tempers a shallow notare or gunome base into which enter ko-gunome, ko-chōji and pointed togariba, with abundant ashi and yō. The nioiguchi is deep and bright, ko-nie adheres well with passages of rougher nie, and kinsuji and sunagashi run freely, small tobiyaki and yubashiri scattered along the edge. The bōshi runs midare-komi, rising to a pointed tip with hakikake or turning back in a small ko-maru. The construction is the full Nanbokuchō build, wide in mihaba with little width-taper, thick in kasane, an extended chū-kissaki or an ō-kissaki, hand-heavy and imposing.

The jigane carries the Bizen credential that keeps the work from turning purely Sōshū. Itame with thick ji-nie and well-entering chikei appears on every blade, and over it stands a midare-utsuri, clear where the forging is itame with mokume and falling to a faint utsuri-like cast on the rest. On the signed register, by contrast, the hand is tighter and calmer. The dated tachi run to a well-packed itame with fine ji-nie and only a light utsuri, the temper a chū-suguha or suguha-toned line mixed with ko-gunome and ko-chōji, even saka-ashi entering, ko-nie and ko-ashi present. Devotional carving, bonji set at the koshimoto, appears on more than one piece.

The published sources draw two further registers within his own work. On the signed tantō they read a more emphatic Sōshū cast than Chōgi himself, noting that 'among the signed survivors the tantō press the Sōshū manner further than Chōgi'[[c:2]]; these are hira-zukuri with a standing hada, a small notare with gunome growing vigorous toward the tip, sunagashi frequent and the pointed bōshi powerful. One signed tantō stands apart from everything else, its temper centered on kataochi-gunome mixed with squared kaku-gunome, evoking Kanemitsu, his circle and even Motoshige rather than the Chōgi midare; the sources call it 'a stylistic range unusual for Nagashige'[[c:3]] and value it as documentary material for the breadth of his manner.

What separates Nagashige from Chōgi is named the same way in entry after entry, and it is the whole of his kantei. His midare is of smaller scale and his yaki somewhat lower, yet 'the nie in both ji and ha surpasses Chōgi's'[[c:4]]; it is on this single recurring point that a Sōden-Bizen blade is converted into a Nagashige attribution. His distinction is carried by his own traits, the smaller, lower midare laid over a ji and ha more richly charged with nie, rather than by any feature borrowed from his brother. Traditionally his son Nagamori carries the line forward in a conspicuously chōji-based but somewhat lesser hand.

Fujishiro grades him Jō-jō saku. Signed, ubu Nagashige are extremely rare, and the body of his record runs through the Tokubetsu Jūyō and Jūyō tiers and the prewar Jūyō Bijutsuhin, above which stands his single National Treasure, the Kenmu 1 tantō held in the Hon'ami family. Several blades carry daimyō provenance: a katana given by Tokugawa Ieyasu to the Naruse house of Inuyama in Owari and long kept there, others through the Maeda of Kaga, the Nabeshima of Saga and the Shimazu. With only thirteen blades in the Tokubetsu Jūyō and Jūyō tiers and almost all of them held rather than traded, a signed Nagashige comes to light only seldom; a privately held example, where the broad Sōden-Bizen katana shows its smaller midare over an unusually nie-laden ji and ha, is a notable thing for a collector to encounter, and a document of how Bizen absorbed the Sōshū manner.