The official histories of the Ryukyu Kingdom claim that he was the son of the samurai Minamoto no Tametomo and a local noblewoman during his exile following the Hōgen rebellion.

Tametomo, a historical figure from Kyushu who fought in the Hōgen rebellion during the late Heian period, was exiled to Izu Province after participating in the Minamoto clan's failed assault on the Taira-held city of Kyoto.

He greatly impressed the inhabitants, and briefly ruled over the island; the chief of Ōzato married his daughter to Tametomo, who bore his son Shunten around 1165.

Shortly after Shunten's birth, Tametomo left his family to return to fight in Japan, where he committed suicide after his defeat in battle.

[10] Edo period novelist Takizawa Bakin's Chinsetsu Yumiharizuki [ja] popularized the Tametomo legend throughout Japan and strongly influenced Japanese perspectives on the Ryukyus.

During the Meiji and Taishō era, history textbooks reported Tametomo's journey to Okinawa and Shunten's unification of the island as historical.

Historian Taira Shidehara [ja] described it as "indisputable fact" in 1899, while Shiga Shigetaka supported the Shō dynasty's genealogical links to Shunten and Tametomo in a 1904 geography textbook.

[11] Katō Sango (1865–1939) published a scholarly critique of the narrative in 1906, describing it as a hoax created by Shō Shōken in the Chūzan Seikan.

[13] In 2020, Yoshinari Naoki theorized that the Shunten legend represented a memory of groups of Japanese traders on Kikaijima who moved southward to Okinawa after its invasion by the forces of Minamoto no Yoritomo in 1188.