The second-generation Iyo no Jo Munetsugu of appears in the designated record only under his early name. Each of his four blades is signed no junin Minamoto Muneyasu, a long signature cut toward the on the in a fine chisel and a distinctive hand, and the published sources note that the manner of the signature itself shows the marks of the Iyo no Jo line.
Who Muneyasu was has been argued in the reference works. The Bengi wrote only "perhaps a pupil of Iyo no Jo, the first generation" (伊予掾(初代)門人ならむか), and the Ichiran and Kokon Kajibiko likewise counted him among the first Iyo no Jo's pupils. The prevailing view today, the published sources state, takes Muneyasu as "the early name of the second-generation Iyo no Jo Munetsugu". It rests on a naming warrant in which the lord Nabeshima Katsushige bestowed the name Muneyasu on the ninth day of the ninth month of Kan'ei 9. One earlier commentary was more cautious. It noted a theory that Muneyasu was the same man as Masatsugu, found no evidence for it, and would say only that he was the smith most closely tied to the first Iyo no Jo.
His work keeps to the line's manner. Over a closely packed or , at times mixed with flowing grain, the adheres and the enter well. The temper is a varied of with , -like and pointed elements. and enter, the is deep and the strong and thick, and and run through it, with -like near the tops of the temper. The published sources judge this a range "shared in both and with the first-generation Munetsugu", a manner aimed at like the first generation's. One commentary finds in the soft brightness of the , produced by fine , a natural taste recalling old works.
The is where the four blades lean their own way. On three of them it resolves in a or a -like tip with a rather long return, at times after entering , where the first generation's mostly turn broadly. With so small a record this is a tendency, not a rule.
Few works signed Muneyasu survive, and the published sources value them as much for what they settle as for their quality: they illuminate Muneyasu's own work and its relation to the second-generation Munetsugu, and they serve the study of a line that held a distinctive place among swords. All four stand in the tier, and provenance is not recorded for any of them. A signed Muneyasu is therefore an uncommon encounter, a document of the Iyo no Jo succession that comes to light only now and then.