Details of his birth, death, and deeds remain unclear. Tradition identifies him as the grandfather of Sho Hashi, first king of the unified Ryukyu Kingdom, and holds that he crossed to Izena Island on his father Yakura Ufunushi's orders and built Izena Castle there. His son Sho Shisho (father of Sho Hashi) later became lord of Sashiki, laying the groundwork for Sho Hashi's unification of the three kingdoms. Samekawa Ufunushi's own historicity remains within the realm of tradition, and some scholars suggest he may be a later invention of genealogical records.

As a figure known only through tradition, no concrete portrait of his character survives, but he is positioned as the grandfather of the founding king and remembered as the starting point of the First Sho dynasty's story, beginning on Izena Island.

Izena Island is closely tied in origin legends to both the First Sho dynasty (which produced Sho Hashi) and the Second Sho dynasty (which produced King Sho En, born Kanamaru). Izena Castle, traditionally said to have been built by Samekawa Ufunushi, survives today as the setting of this legendary story.