Yoshimitsu, known as Tōshirō Yoshimitsu (藤四郎吉光), is regarded as the culminating master of the lineage of Yamashiro Province, active in the late period. Traditionally held to have been a disciple of Kuniyoshi, he is celebrated — together with Kunimitsu of — as a supreme maker of . In the period he was further acclaimed alongside Masamune and Gō as one of the "Three Great Works of the Realm" (Tenka Sansaku), and moreover "was placed foremost among them and was most highly treasured." No fewer than thirty-eight of his works appear in the Kyōhō Meibutsu-chō, an extraordinary concentration that attests to his preeminence. Although overwhelmingly known for short blades, the exceedingly rare -type works attributed to him — most notably the Ichigo Hitofuri Tōshirō — constitute precious source material for the study of early mounted-sword forms.
Yoshimitsu's forging exhibits two recognized modes: one is an extremely fine grain known as (pear-skin texture), tightly compacted and lustrous; the other is a comparatively larger-grained in which the stands prominently. In both types, fine adheres thickly across the surface, accompanied by , and the steel characteristically shows a moist, clear quality — what the consistently describes as possessing ("a moist/soft quality") while being "strikingly clear." appears in many examples. His forte is , executed in , with the bright and clear. Recurring hallmarks include small linked appearing around the (lower section), a narrowing of the tempered width around the , and — beneath the — the linear "dropping down" or "biting down" of known as , a trait the regards as a salient point of appreciation. Fine , , and interweave within the , and the typically gathers into a neat . His forms are "remarkably varied": broad and compact; slender yet elongated; broad and elongated; and standard proportions — a range that closely accords with the work of his teacher Kuniyoshi, such that "the connection between the two is readily accepted."
Across assessments, Yoshimitsu's work is described as displaying "the highlights of Yoshimitsu's art" and as "clearly revealing the strengths and points of special interest characteristic of this smith." The designation records consistently emphasize that his pieces are — sound and well-preserved — and that his calligraphic signature, executed in large, fluent characters with a fine chisel, is "highly esteemed as unrivaled throughout the history of sword inscriptions." Within the school, the distinguishes his individuality from the lineage by noting that "the in both and is applied more thickly and is felt more strongly." He stands as the last and greatest expression of the tradition — a smith who, in the institutional judgment of the , brought his lineage "to its culminating brilliance."