Kaio's dramatic 93rd-minute winner helped Jeonbuk Motors beat Seoul 1-0 and move to the brink of securing the K. League title.
Jeonbuk held a 10-point lead over second-placed Suwon Bluewings as the K. League split into the Championship and Relegation Round this weekend.
The Bluewings' 3-0 win over Ulsan on Saturday briefly closed that gap, but Jeonbuk re-established their margin in Sunday's encounter in South Korea's capital.
For the majority of the game it looked as though Jeonbuk would be held to a frustrating stalemate at the Seoul World Cup Stadium, until Kaio's timely intervention.
Choi Kang-hee's men can now secure a third league title in six years by beating Jeju United next Sunday.
The Bluewings are refusing to give up the ghost, though. Their victory was kickstarted started by an own goal from Ulsan's Lee Jae-won, before Santos Junior and Lee Sang-ho added further gloss at the Munsu Cup Stadium.
In Saturday's only Championship Round fixture, Jeju United moved into fourth thanks to 1-1 draw with Pohang Steelers.
Sangju Sangmu remain bottom of the Relegation Group as they fell to a 3-2 defeat at home to Busan I'Park on Sunday.
Busan's win means they are now four points clear of fifth spot in the Relegation Group. The team that finishes second bottom will play a relegation/promotion play-off.
That position is currently occupied by Gyeongnam, who could only muster a 1-1 draw at Incheon United on Sunday.
Gyeongnam remain level on points with Seongnam, though, after they were held 1-1 at Jeonnam Dragons.