Uichiro Onishi was born in Osaka in 1891. His family name was Hosokawa.
A disciple of Grand Champion Hitachiyama, he made his debut in the arena (1910), became a champion (1916) and 21st Grand Champion (1917). His rapid rise to the top rank in sumo wrestling even surpassed his master's. He won 88 per cent of all bouts hefought since he became Grand Champion a percentage which was equaled by Grand Champion Tachiyama.