Muneyoshi is a smith of the Ko-, the earliest generation of the , working in the opening years of the period. The published sources place him at the threshold of the school: drawing on the Meizukushi Taizen, they record that 'Muneyoshi belonged to the Ko-', that he was a son of Munekuni and married into the house of Norimune, 'son-in-law of Norimune, founder of the ', and that he served alongside Norimune and Sukemune as one of the , the swordsmiths in monthly attendance on Retired Emperor Go-Toba. One entry identifies him with the smith the places around the Jōkyū years (1219-22) and records him as a of Go-Toba's seventh-month rotation; a gives him the Shōji-era rotation.
His blades are , slender and well-proportioned, several retaining a high and strong even where shortened. Over an , at times a closely packed and mixed with , the steel carries a thick and a vivid that stands out clearly on every blade whose is described. The temper is the tell of his hand: not the full clove-flower of the later school but a -toned small , into which he sets and , with abundant and , well adhered, and fine and running through. The runs straight into a small or finishes in a -like sweep.
The is the constant. with and a bright appears on each fully described blade, sometimes with entering frequently and the grain standing a little, and on one the forging tightens into with . Over that the stays comparatively calm. Where one piece widens into a more flamboyant toward the middle with , the body of the temper remains a small irregular line, deep in and , the activity carried in and rather than in towering clusters.
The published sources draw a careful distinction within his own work. Examining extant signed pieces, they find that the manner of the signature differs from blade to blade, and that the workmanship divides in two: some are archaic and classical in a mode, others mix in for a somewhat more decorative feeling. From this they infer that 'there were multiple smiths' using the one name Muneyoshi. The point recurs across his entries and is the central scholarly question around him, left open for further study. The commentary on the two recorded in Honma's inventory of the Imperial collection reaches the same view, that he was "not one man, but that there were others of the same name". Of that pair, the shortened blade has a brilliant over and a mixed with and , for this smith a work of good and flamboyant execution. The blade is quieter, a -toned temper with and . The two signatures look much alike, yet on close inspection "differ considerably in the handling of the chisel".
What separates the Ko- Muneyoshi from both his neighbours is exactly what the judges name. He is set apart from the flamboyant of the mid- to late- , his temper read instead as 'an archaic register, unlike the flamboyant of the mid-, with the old colour of its period'. His own marks are the bright in the and the gathering on a -toned edge, the features the published sources sum up as making the Ko- character plain.
For the collector he is a rare early name. Fujishiro grades him Jō-jō . He has no National Treasures; his record runs instead through Important Cultural Properties, and the higher modern tiers, and the published commentary calls one shortened 'foremost among works by the same hand'. His blades are preserved in long-held collections and institutions grounded in their own provenance, the Mōri family among the houses, the Seikadō Bunko from the Iwasaki collection, and the Kurokawa Institute of Ancient Cultures, with a pair held at Atsuta Jingū. Two more signed , presented to the Emperor Meiji by the Matsukata and Sagara families, are recorded in Honma's inventory of the Imperial collection. Those two signed are Important Cultural Properties, known by their plates, one tempered in mixed with , the other in . Honma noted that the signature of one of them is almost the same as that of the Seikadō . Only a small number fall in the and tiers, so a signed Ko- Muneyoshi comes to light only seldom, and a privately held example is a notable thing for a collector to encounter, a document of how the began.