Narimune (成宗) is transmitted as the second son of Norimune, the founder of the Fukuoka lineage in Province. Active in the early period, he belongs to the group of smiths — including Sukemune, Hisamune, Muneyoshi, Munetada, Shigehisa, and Sadazane — who are separately referred to as "Ko-." The manner of workmanship seen in these smiths differs from the splendid, ornate style of the mid- masters; in and in the workmanship of and , they strongly preserve the flavor of work. His blades characteristically present a slender form with shallow and , often with pronounced that produces an especially handsome overall silhouette.
Narimune's forging is a dense mixed with , bearing minute and fine , with conspicuous or standing out in the . The is based on mixed with ; abundant and appear, adheres well, and and are frequently seen. The tends toward with a rounded turn-back. In signed examples the tang preserves a two-character . The observes that while his work evokes an archaic elegance, the is notably well-knit with clearly standing , and the — centered on and showing variations in the — vividly reveals the appearance of Ko-.
Narimune's works are praised as displaying the distinctive points of interest characteristic of Ko-. Though calm in feeling, they are blades in which one can fully appreciate the qualities of the early Fukuoka tradition. The and are consistently described as — sound and well-preserved — and of good quality. Several examples bear distinguished provenance, including blades formerly transmitted within the Tokugawa shogunal house and others held in the Imperial Collection. His oeuvre stands as a typical and authoritative representation of the early school at its most refined.