Motomitsu was a swordsmith of the Bizen Osafune school in the Nanbokuchō period, transmitted as either a son of Kanemitsu or a smith trained in his circle, and recorded as having held the title Saemon-no-jō. His dated works run from the Kōei era through Eiwa, so the span of his activity is securely fixed, and the published sources open the Tokubetsu Jūyō tachi held by the Tokugawa house plainly: "a signed tachi by Motomitsu, a pupil of the master"[[c:1]]. He carries the Kanemitsu manner forward into the second half of the fourteenth century, and the same commentary that places him in that lineage also draws the careful line that defines his standing within it.

His hand is read first in the temper. Over an itame he sets a gunome-dominant midare whose spine is kataochi-gunome, the saw-tooth pattern of the Kanemitsu workshop, and into it he crowds angular teeth, togariba, and shallow ko-notare whose crests turn angular. The published sources name this intermixture as his own: of the Tokugawa tachi they write that "the workmanship is broadly Kanemitsu-den, yet, as in this blade, the gunome are conspicuous, and his distinctive character is seen in the way gunome of many shapes mingle together"[[c:2]]. The figure recurs across his Jūyō entries, set against the more orderly, linked gunome the school also produced. Ashi and yō enter, the nioiguchi tightens and runs bright with ko-nie, and kinsuji and sunagashi play through the ha.

The jigane is the constant beneath that temper. His itame is mixed with mokume and frequently tends to stand into hada-dachi, with ji-nie, fine chikei, and patches of jifu-toned steel, over which a midare-utsuri rises; near the edge it often reads instead as a straight, sugu-toned utsuri, the Osafune jigane he shares with his master. The bōshi enters in midare-komi and turns with a pointed tendency to a small round, finishing with fine hakikake. On his dirks he carves bō-hi, or a koshi-hi with accompanying soe-hi, and one tantō carries a devotional gomabashi, the quiet decorative vocabulary of late Osafune.

His record divides cleanly by form. On one side stand the signed, dated blades in his own hand: tachi cut Bishū Osafune Motomitsu, and the hira-zukuri wakizashi and tantō, several of them ubu and crisply dated to Bunna, Jōji and Ōan, of which the published sources say "the quality of the workmanship gives the sense of approaching Kanemitsu"[[c:3]] and which they prize as research material for the smith. On the other stand the ō-suriage mumei katana, wide in body with little taper and an extended chū-kissaki, the grand Nanbokuchō shape, judged to him from era and the Kanemitsu manner. The commentary notes that signed tachi by him are comparatively few.

What separates him from the rest of the group is exactly what the judges name when they affirm an unsigned blade. They find in the standing grain and the varied teeth within the kataochi-gunome the features that mark a work as his, writing of one katana that "within the Kanemitsu group there is that which should be most closely likened to Motomitsu, and the attribution is correctly affirmed"[[c:4]]. Yet they are equally candid about his rank: in overall standing "there are points where he yields slightly to Kanemitsu"[[c:5]]. His is the able second hand of the workshop, holding its temper while pressing his own crowded, varied gunome upon it, and the unsigned attributions rest on school and period rather than on a single decisive personal tell.

For the collector he is a documented but uncommon late-Osafune name. The Tōkō Taikan values him at the upper-middle level, and his connoisseurship record is built less on volume than on the precision of his dated, signed work. He has no National Treasures; his standing rests instead on one Important Cultural Property, a signed tachi preserved in the Mitsui Bunko in Tokyo, together with one Tokubetsu Jūyō and a body of Jūyō blades, some thirty-eight in the Tokubetsu Jūyō and Jūyō tiers in all. The provenance that survives is good: the Tokubetsu Jūyō tachi descends through the Tokugawa house, called by the published sources "a superior work by Motomitsu transmitted in the Great Tokugawa family"[[c:6]]; a katana bearing a gold-inlaid attribution thought to be the work of Hon'ami Mitsutada is held by the Sano Art Museum, formerly in the Homma collection. Most designated Motomitsu blades are held rather than traded, so a signed example comes to light only from time to time, and when one does it is a precise, datable record of how the Kanemitsu workshop carried Osafune through the Nanbokuchō age.

Motomitsu was a swordsmith of the Bizen Osafune school in the Nanbokuchō period, transmitted as either a son of Kanemitsu or a smith trained in his circle, and recorded as having held the title Saemon-no-jō. His dated works run from the Kōei era through Eiwa, so the span of his activity is securely fixed, and the published sources open the Tokubetsu Jūyō tachi held by the Tokugawa house plainly: "a signed tachi by Motomitsu, a pupil of the master"[[c:1]]. He carries the Kanemitsu manner forward into the second half of the fourteenth century, and the same commentary that places him in that lineage also draws the careful line that defines his standing within it.

His hand is read first in the temper. Over an itame he sets a gunome-dominant midare whose spine is kataochi-gunome, the saw-tooth pattern of the Kanemitsu workshop, and into it he crowds angular teeth, togariba, and shallow ko-notare whose crests turn angular. The published sources name this intermixture as his own: of the Tokugawa tachi they write that "the workmanship is broadly Kanemitsu-den, yet, as in this blade, the gunome are conspicuous, and his distinctive character is seen in the way gunome of many shapes mingle together"[[c:2]]. The figure recurs across his Jūyō entries, set against the more orderly, linked gunome the school also produced. Ashi and yō enter, the nioiguchi tightens and runs bright with ko-nie, and kinsuji and sunagashi play through the ha.

The jigane is the constant beneath that temper. His itame is mixed with mokume and frequently tends to stand into hada-dachi, with ji-nie, fine chikei, and patches of jifu-toned steel, over which a midare-utsuri rises; near the edge it often reads instead as a straight, sugu-toned utsuri, the Osafune jigane he shares with his master. The bōshi enters in midare-komi and turns with a pointed tendency to a small round, finishing with fine hakikake. On his dirks he carves bō-hi, or a koshi-hi with accompanying soe-hi, and one tantō carries a devotional gomabashi, the quiet decorative vocabulary of late Osafune.

His record divides cleanly by form. On one side stand the signed, dated blades in his own hand: tachi cut Bishū Osafune Motomitsu, and the hira-zukuri wakizashi and tantō, several of them ubu and crisply dated to Bunna, Jōji and Ōan, of which the published sources say "the quality of the workmanship gives the sense of approaching Kanemitsu"[[c:3]] and which they prize as research material for the smith. On the other stand the ō-suriage mumei katana, wide in body with little taper and an extended chū-kissaki, the grand Nanbokuchō shape, judged to him from era and the Kanemitsu manner. The commentary notes that signed tachi by him are comparatively few.

What separates him from the rest of the group is exactly what the judges name when they affirm an unsigned blade. They find in the standing grain and the varied teeth within the kataochi-gunome the features that mark a work as his, writing of one katana that "within the Kanemitsu group there is that which should be most closely likened to Motomitsu, and the attribution is correctly affirmed"[[c:4]]. Yet they are equally candid about his rank: in overall standing "there are points where he yields slightly to Kanemitsu"[[c:5]]. His is the able second hand of the workshop, holding its temper while pressing his own crowded, varied gunome upon it, and the unsigned attributions rest on school and period rather than on a single decisive personal tell.

For the collector he is a documented but uncommon late-Osafune name. The Tōkō Taikan values him at the upper-middle level, and his connoisseurship record is built less on volume than on the precision of his dated, signed work. He has no National Treasures; his standing rests instead on one Important Cultural Property, a signed tachi preserved in the Mitsui Bunko in Tokyo, together with one Tokubetsu Jūyō and a body of Jūyō blades, some thirty-eight in the Tokubetsu Jūyō and Jūyō tiers in all. The provenance that survives is good: the Tokubetsu Jūyō tachi descends through the Tokugawa house, called by the published sources "a superior work by Motomitsu transmitted in the Great Tokugawa family"[[c:6]]; a katana bearing a gold-inlaid attribution thought to be the work of Hon'ami Mitsutada is held by the Sano Art Museum, formerly in the Homma collection. Most designated Motomitsu blades are held rather than traded, so a signed example comes to light only from time to time, and when one does it is a precise, datable record of how the Kanemitsu workshop carried Osafune through the Nanbokuchō age.