Yukimitsu (行光) was a swordsmith of Province active during the late period. He trained under Kunimitsu, the founder of the Sōshū-den, and together with his fellow students Masamune and Norishige, further developed and brought that tradition toward completion. The consistently describes Yukimitsu as "somewhat senior to Masamune," establishing his position as the eldest among Kunimitsu's principal disciples. Extant signed works are extremely few and are limited exclusively to , all bearing a two-character signature in gyōsho style. Classical sword treatises such as the Nōami-bon and Genki-bon record that his range of workmanship was broad, encompassing not only but also , -based irregular tempering, and even . However, among unsigned blades bearing attributions to Yukimitsu, or shallow, gentle predominate, and the overall character of the and tends to reflect the manner of Kunimitsu.
Yukimitsu's forging characteristically shows mixed with , frequently with a or tendency. The descriptions consistently note that adheres thickly in exceedingly fine particles, that enter densely and frequently, and that appears on certain . His ranges from with slight tendencies and mixed , through shallow -based patterns with and , to more pronounced . Across all modes, adheres thickly; and run conspicuously and frequently; and appear along the ; and the is invariably described as "bright and clear." The often enters in or with , at times becoming flame-like. Several specifically identify the thick, luminous as "characteristic of higher-ranking Sōshū-den works." Signed in particular demonstrate workmanship directly connected to Kunimitsu, including the sometimes termed "Okina no hige" — the old man's beard — a feature that recalls Kunimitsu himself.
The repeatedly affirms that what unites the diversity of Yukimitsu's output is that "both and are richly covered with , and the activities of , , and stand out prominently, fully displaying the subtle fascination of workmanship." This phrase, recurring across decades of designations, constitutes the essential evaluative formula for the smith. Works are praised for steel that is "clear and bright," for forging that is "powerful" with "densely interwoven," and for preservation that is — sound and well-preserved — with abundant . Even structural details such as narrow are noted as presenting "points of interest characteristic of work." Yukimitsu is thus positioned as a master who inherited the foundation and, through the heightened expression of and its attendant phenomena, helped establish the tradition at its highest level of refinement. Among the finest examples, individual blades are singled out as ranking "among the most outstanding" attributed to this smith — testimony to his standing as one of the supreme practitioners of the school.