Yokozuna Hakuho improved to a perfect 8-0 to maintain a one-win lead as the New Year Grand Sumo Tournament reached its midpoint on Sunday.

The sole remaining yokozuna in action, Hakuho has now won 26 straight bouts, excepting his forfeit on Day 4 of July's grand tournament. Although he started the 15-day event at Tokyo's Ryogoku Kokugikan with a series of near misses, his form has improved since yokozuna Kisenosato retired and yokozuna Kakuryu pulled out with an injury.

Hakuho entered his match against the 198-kilogram Aoiyama (5-3) having beaten him in 18 of their 19 career bouts. The Bulgarian maegashira kept the yokozuna's hand off his belt and surged forward aggressively, sticking his right arm inside to wrap up Hakuho's torso as a precursor to a force out.

Despite being under pressure, the Mongolian master coolly executed a pulling overarm throw that sent Aoiyama tumbling forward.

"I know it's no good putting my arm inside, but it's my habit," Aoiyama said.

Hakuho is in the hunt for his 42nd championship and his first since going 15-0 in September. He missed November's tournament due to injury.

With Emperor Akihito and Empress Michiko in attendance, Hakuho's victory was the last they will see live prior to the emperor's abdication on April 30.

No. 8 maegashira Kaisei, No. 13 Yago and No. 15 Chiyonokuni all improved to 7-1, while Onosho, who started the day at 6-1, lost to November's champion, sekiwake Takakeisho (6-2).

Kaisei earned his seventh win by defeating personal nemesis Kotoshogiku. The former ozeki Kotoshogiku dodged the big Brazilian's charge and pressed him back to the straw. But the 204-kg Kaisei sidestepped along the straw-bale ridge and toppled Kotoshogiku with a beltless arm throw.

Kotoshogiku's second career loss to Kaisei in 12 bouts left the No. 4 maegashira with a 4-4 record.

Yago won his sixth straight bout in a match that overcame an artless opening. The makuuchi debutant rocked Daiamami (2-6) back on the charge with a shoulder to the head, but shot past his opponent, and avoided being shoved out from behind with a spin move.

Back on level terms, Yago outfought Daiamami at the belt to secure a two-handed hold and force him out.

Chiyonokuni followed Yago into the ring and finished a slapping and shoving skirmish by taking a step back and slapping Kagayaki (1-7) down when the No. 12 maegashira pursued with his weight too far forward.

Ozeki Goeido's rollercoaster tournament took a dip as he lost to sekiwake Tamawashi to fall to 3-5. Goeido had followed his opening four-match losing streak with three straight wins, but was on the defensive from the start against his Mongolian opponent, who improved to 6-2 to remain in the hunt for his first championship.

The other ozeki, Takayasu (4-4), was the victim of a rocket-like charge from Shohozan (3-5). The No. 3 maegashira got around Takayasu's left flank before the ozeki could react and sent him stumbling to the sandy surface.

"I was able to win by moving so he couldn't get a belt hold," Shohozan said. "As I was moving after we collided, I got around on his side better than I thought I would."