Hakuho took sole possession of the lead yesterday after rank-and-filer Aminishiki stunned Asashoryu by sending him to his first loss in Japan's Summer Grand Sumo tournament.
Ozeki Hakuho, who is bidding for promotion to grand champion, toppled fourth-ranked maegashira Tochiozan to extend his record to 10 wins.
Tochiozan fell to 4-6 in the 15-day tourney.
Hakuho, who had been tied for the lead with fellow Mongolian Asashoryu, won the Spring tournament.
Capturing the Emperor's Cup in this tournament would ensure promotion to grand champion.
Aminishiki defeated Asashoryu in the day's final bout at Ryogoku Kokugikan, sending the grand champion flying out as he tried to tug at Aminishiki at the ring's edge.
Asashoryu's record fell to 9-1, while Aminishiki improved to 7-3.
In other major bouts, sekiwake Kotomitsuki stayed on pace with one loss after toppling rank-and-filer Kisenosato, who fell to 4-6.
Chiyotaikai engaged in a fierce slapping battle with fellow ozeki Kaio before pulling the latter down, bringing both wrestlers' records to 8-2.
Mongolian sekiwake Ama upset Bulgarian Kotooshu, working his way quickly behind the ozeki to send him out.
Ama evened his record at five wins and losses, while Kotooshu dropped to 7-3.
Top-ranked maegashira Tokitenku made short work of Kotoshogiku, improving his record to 5-5 while the komusubi fell to 4-6.
Komusubi Toyonoshima traded a flurry of moves and jumps with Kakizoe before easing the latter out for his second win of the tournament. Kakizoe remained winless at 0-10.