Recalled wild child Bernard Tomic was the hero for Australia and Tatsuma Ito sealed a pulsating tie for Japan as both countries reached the Davis Cup World Group play-offs on Sunday.
Tomic, back in the fold after being dropped for disciplinary reasons, beat Denis Istomin to give Australia an unassailable 3-1 lead in their Asia/Oceania Group I tie with Uzbekistan, after also winning his first singles match on Friday.
In Tokyo, 24-year-old Ito held his nerve to defeat South Korea's Cho Min-Hyeok 6-3, 6-3, 6-0 in the decisive match, after rookie Lim Yong-Kyu upset Japan's Go Soeda to leave the fixture poised at 2-2.
"I tried to play 100 percent," Ito said. "I did my best from the beginning until the end."
Australia and Japan now go through to the World Group play-offs in September where they will try to seal a spot in the global team competition's top tier next season.
Meanwhile India and China enjoyed 5-0 whitewashes respectively against Indonesia and Taiwan, who will contest a relegation tie in September with the loser dropping to Asia/Oceania Group II.
Australia's captain Pat Rafter has endured a rocky relationship with Tomic, who has had a fractious relationship with senior tennis figures and several run-ins with the law.
But Rafter was full of praise for the 20-year-old, Australia's top player at world number 43, after he battled back from a set down to win 4-6, 6-2, 6-2, 6-3 against the 46th-ranked Istomin, following Friday's win over Farrukh Dustov.
"Bernie played some of the best tennis I've seen him play," Rafter told Australian Associated Press. "To play two great matches in a row now, that was really important for him.
"Everything went perfectly, it's actually ridiculous how (perfect) it was. I'm very proud of the guys."
India also put internal problems behind them, after fielding a weakened line-up in their opening defeat to South Korea during a row over pay and conditions, as they stretched their Davis Cup record to 6-0 against Indonesia.
Veteran doubles specialist Leander Paes and partner Sanam Singh settled the tie on Saturday with a straight-sets victory, after Somdev Devvarman and Yuki Bhambri had given the hosts a 2-0 lead on the opening day.
China also preserved their place in Asia/Oceania Group I next season when Zhang Ze and Wu Di spearheaded the one-sided victory over Taiwan by winning both their singles matches in Tianjin.
Elsewhere, Pakistan said they would protest after their Asia/Oceania Group II tie was awarded to opponents New Zealand because of an unplayable surface at a neutral venue in Myanmar, which was hosting the fixture for security reasons.
Pakistan had won the first singles and Aisam-ul Haq Qureshi was leading in the second on Friday when the referee stopped the tie and declared it abandoned, awarding it to New Zealand as the courts were Pakistan's responsibility.
"We are devastated... we are going to lodge a protest against the decision," Pakistan Tennis Federation president Kaleem Imam told AFP.