According to the ancient Japanese chronicles Kojiki written in 680 and Nihon Shoki written in 720, ?jin was the son of the Emperor Ch贖ai and his consort Jing贖. As Ch贖ai died before ?jin's birth, his mother Jing贖 became the de facto ruler. These sources allege that ?jin was conceived but unborn when Ch贖ai died. His widow, Jing贖, then spent three years in the conquest of Korea, then, after her return to Japan, the new emperor was born, three years after the death of the father.

Ojin became the crown prince at the age of four. He was crowned (in 270) at the age of 70 and reigned for 40 years until his death in 310. He supposedly lived in two palaces both of which are in present day Osaka. ?jin is traditionally identified as the father of Emperor Nintoku, who acceded after ?jin's death.

?jin has been deified as Hachiman Daimy?jin, regarded as the guardian of warriors. The Hata Clan considered him their guardian Kami. The actual site of ?jin's grave is not known, but he is traditionally venerated at a memorial Shinto shrine (misasagi) at Osaka.

The Imperial Household Agency designates this location as ?jin's mausoleum. It is formally named Eega no Mofushi no oka no misasagi.