Hakuho overpowered Okinumi to get his bid for an eighth consecutive title back on track and set up an intriguing run at the Nagoya Grand Sumo Tournament on Thursday.
Stunned by ozeki hopeful Kotoshogiku on Wednesday, the Mongolian yokozuna showed no mercy in the day's final bout, blasting out his fourth-ranked opponent with maximum efficiency at Aichi Prefectural Gymnasium.
Hakuho (11-1) remains one win behind ozeki and compatriot Harumafuji, who preserved his flawless record by getting a firm grip on the front of Kaisei's belt and yanking the Brazilian-born grappler (6-6) around and down to the clay surface.
Kotoshogiku and Estonian ozeki Baruto shared third place at 10-2.
Kotoshogiku stayed on course for a move up to sumo's second rank of ozeki, biding his time before bellying out fellow sekiwake Kakuryu (7-5) to move into double digits.
Kotoshogiku is likely to need at least two more wins here to be considered for promotion, although his slaying of Hakuho will have given him bonus points.
A move up the rankings would see the 27-year-old fill the void left by Kaio, who retired just days after surpassing former yokozuna great Chiyonofuji as the all-time wins leader on the fifth day with his 1,046th victory.
The 38-year-old Kaio's retirement after an illustrious but injury interrupted career leaves sumo without any Japanese in the top two ranks for the first time since the 1993 New Year basho. Americans Akebono and Konishiki reigned at ozeki at that time when there was no yokozuna
In other matchups, Baruto dodged a bullet to thrust fourth-ranked Takekaze off the dohyo and keep alive his slim title hopes, but Bulgarian Kotooshu was slapped down to a fourth loss by sekiwake Kisenosato (7-5).