Mitsuyo (also read Kosei) was a smith of the Miike school lineage, originally rooted in Chikugo Province. By the period, later generations of this line had dispersed to various provinces, and at least one branch relocated to Aki Province. A dated bearing the inscription "Aki no ju" with a Meitoku 2 (1391) date provides direct documentary evidence of this migration. The regards this relocation as a matter of considerable historical significance and describes such works as "extremely valuable material" for understanding the school's geographic diffusion. The dedicatory inscriptions appearing on certain Aki Province works -- naming figures such as Sanechika and Minechika -- remain unidentified, adding a layer of provenance interest to these pieces.
Mitsuyo's characteristic forging is flowing toward -gakari with a standing grain tendency, enlivened by and the presence of . The temper is consistently a narrow or in , with a slight tendency and minimal ; enters within the hardened edge. The characteristically shows turning to . Blade forms range from with uchi-zori and somewhat thick to broader, thinner pieces with shallow curvature consistent with -period proportions. Carvings include above and with in relief.
The appraises Mitsuyo's workmanship as "superior" and judges it "on par with later Miike school work," situating these pieces squarely within the established technical and aesthetic standards of that lineage. Imperial provenance -- transmission through the Katsura-no-miya family -- attests to the esteem in which certain examples have been held. Within the broader Miike tradition, Mitsuyo represents the school's continued vitality during the era and its capacity to maintain a refined, -based idiom even as the lineage extended into new provincial workshops.