TOKYO (Kyodo) -- Joint overnight leader Oho reeled off another high-caliber victory Friday after the New Year Grand Sumo Tournament was rocked by news of yokozuna Terunofuji's retirement.

The departure of the Mongolian-born Terunofuji, announced by the Japan Sumo Association earlier on Day 6 of the 15-day tournament, leaves the ancient sport without an active grand champion for the first time in 32 years.

The 10-time Emperor's Cup winner decided to bring down the curtain on his injury-plagued career after struggling through the first four days and pulling out on Day 5 at Tokyo's Ryogoku Kokugikan arena.

Current yokozuna promotion candidate Hoshoryu and fellow ozeki Onosato bounced back from their upsets of the previous day, but the nightmare continued for Kotozakura, who dropped to 1-5 as rank-and-filer Atamifuji claimed his second ozeki victim in a row.

No. 3 maegashira Oho, bidding for his maiden promotion to the three "sanyaku" ranks below yokozuna, improved to a perfect 6-0 by pushing out No. 2 maegashira Tobizaru (4-2).

Having earned each of his wins against current or former sanyaku opponents, the 24-year-old grandson of former yokozuna Taiho shares the lead with No. 5 maegashira Chiyoshoma and No. 14 maegashira Kinbozan, both of whom beat fellow rank-and-file wrestlers.

A day after his first loss at the hands of Atamifuji, Hoshoryu (5-1) got back on the winning track with a rear push out against No. 3 maegashira Gonoyama (4-2).

Onosato (3-3) physically overwhelmed No. 4 maegashira Shodai (2-4), beating the former ozeki by force out.

Kotozakura was forced out in a do-over by No. 2 maegashira Atamifuji (2-4) after the judges handed the struggling ozeki a lifeline.

The initial bout between the pair, which Atamifuji appeared to have won in similar fashion, was ordered to be refought after a ringside official prematurely signaled that Kotozakura had stepped out.