Tosanoumi upset Kaio at the New Year Grand Sumo Tournament on Wednesday, dashing any hope the ozeki wrestler had for promotion to sumo's highest rank.
No. 2 maegashira Tosanoumi sidestepped Kaio at the faceoff and then swatted the struggling ozeki down to improve to 2-2.
Kaio, who needed at least 13 wins in this tournament to get consideration for promotion to grand champion, was handed his third straight loss and fell to an unseemly 1-3.
Touted as a candidate for promotion to yokozuna before the start of the 15-day meet at Ryogoku Kokugikan, Kaio is now struggling just to survive another day.
Elsewhere, Mongolian grand champion Asashoryu remained in the driver's seat at a perfect 4-0 when he dispatched top maegashira Tochinonada in the day's final bout.
Asashoryu won five of six tournaments last year and hasn't shown any signs of slowing down. Lower-ranked wrestlers Asasekiryu and Tamakasuga also stand at 4-0. Tochinonada has a 2-2 record.
Mongolian Hakuho, who upset Kaio on Tuesday, won his third straight bout since losing to Asashoryu on the opening day.
Komusubi Hakuho used a barrage of arm thrusts before getting a grip of Tamanoshima's belt and lifting the winless No. 3 maegashira out to improve to 3-1.
Wakanosato, who is bidding for promotion to ozeki, was handed his second straight loss when he touched the dirt surface with his hand after forcing fellow sekiwake Tochiazuma to the edge.
Tochiazuma picked up his third win against a sole loss while Wakanosato fell to 2-2.
Ozeki Chiyotaikai improved to 3-1 when he used his trademark arm thrusts to send No. 2 maegashira Kotonowaka out over the straw ridge for his second loss against two wins.
Bulgarian Kotooshu continued to impress with a hard-fought win over seventh-ranked maegashira Hayateumi.
Kotooshu, a No. 4 maegashira, got a hold of Hayateumi's belt after the faceoff and spun the smaller wrestler around several times before using a well-timed leg kick to upend his opponent and improve to 3-1. Hayateumi stands at 2-2.
No. 6 maegashira Kaiho improved to 2-2 after he prevailed in a slap-fest against third-ranked maegashira Kokkai, who has yet to post a win.
Earlier, Russian Roho needed two bouts to improve to 2-2.
In the first bout against Kotonowaka, the ringside judges ruled that both wrestlers went over the raised ring at the same time.
Roho made no mistake when he swatted the ninth-ranked maegashira down after the faceoff. Kotonowaka dropped to 1-3. Mongolian Asasekiryu, at 4-0 , muscled out Kotoshogiku, who dropped to 2-2.