Up-and-coming Onosho upset Harumafuji in his first match against a yokozuna on Thursday, becoming the only wrestler with a perfect 5-0 record at the Autumn Grand Sumo Tournament.
The 21-year-old No. 3 maegashira dodged the Mongolian grand champion's forceful shoves and got him off balance before slapping him down into a forward somersault on the raised dohyo ring on the fifth day of the 15-day tourney at Ryogoku Kokugikan in Tokyo.
"I wanted to tackle the match with courage but without being too worked up, and I was able to do that," said Onosho, who also fought in the day's final bout in the top makuuchi division for the first time.
Asked how he feels to be the sole leader one-third into the tourney, he said, "I don't want to think about that too much. I want to concentrate on taking one bout a day and just do sumo my own way."
Onosho, who on Wednesday beat Terunofuji in his first meeting with an ozeki, handed Harumafuji (2-3), the lone yokozuna competing at this meet, his third straight loss.
Four other wrestlers who began the day with 4-0 records -- top maegashira and former ozeki Kotoshogiku, No. 3 maegashira Chiyotairyu, ninth-ranked maegashira Takanoiwa and No. 11 maegashira Daieisho -- lost their respective bouts.
Chiyotairyu fell to Goeido, who needs eight wins to keep his ozeki status and who improved his record to 4-1 to sit in a seven-way tie one win behind Onosho. Goeido and Onosho are set to meet for the first time Friday.
Terunofuji (1-4), another ozeki looking for a winning record to remain in sumo's second-highest rank, lost to No. 4 maegashira Shohozan (3-2) and walked off appearing in pain in his left knee.
The 35-year-old Yoshikaze (1-4), who returned to the third-highest sekiwake rank for the first time since the Spring tourney in March last year, shoved out second-ranked maegashira Hokutofuji (3-2), who had defeated Harumafuji on Wednesday.
The other sekiwake Mitakeumi (2-3) edged out winless top-ranked maegashira Tochinoshin.
In a battle of two komusubi that saw one false start, Tochiozan picked up his first win of the tourney as he watched Mongolian Tamawashi (2-3) slip and fall amid an exchange of thrusts and throwing attempts.