Perth - Japanese youngster Yasuhiro Koseki has derailed the Australian juggernaut on the opening night of the second BHP Billiton Aquatic Super Series in Perth on Friday night.
With AUD$500 000 up for grabs in the rapid fire five-nation event over two nights, the host nation was expected to dominate through their three current world champions - James Magnussen, Cate Campbell and Christian Sprenger - as they prepare for the upcoming Commonwealth Games in Glasgow in late July.
Up against swimmers from Japan, China, Brazil and South Africa, Australia got off to a flying start through Magnussen and Campbell, who won the men's 100m freestyle and the women's 100m freestyle respectively.
However, the emerging Koseki upset Australian plans by downing Sprenger in the 100m breaststroke.
The two went stroke for stroke for the first 75m, but it was the Japanese swimmer that finished the strongest to win by 0.42sec in a time of 59.94.
Sprenger was second in 1:00.36, with Brazil's Felipe Lima third in 1:01.47.
Koseki, 21, won gold in the same event at the 2013 World University Games in Russia.
There was more delight for the Japanese when exciting teenager Daiya Seto upset 2012 Olympic gold medallist and 2013 world champion Chad Le Clos in the 200m butterfly.
It was the event in which Le Clos rose to prominence at the London Olympics, when the South African touched out American legend Michael Phelps.
However, 19-year-old Seto, the 2013 400m individual medley world champion, came out fast to take a big early lead and never relinquished it to win in commanding fashion in 1:54.82, the South African having to be content with second place in 1:56.45.
Another Japanese teenager, Kosuke Hagino, was very impressive in the men's 200m individual medley, winning in a quick time of 1:55.90 and beating Seto by more than two seconds.
On a good night for the Japanese men, Olympic silver medallist Ryosuke Irie took out the 200m backstroke.
Australia dominated the evening to win 10 of the 17 events and lead the overall points tally.
The Australian efforts were led by freestyler Magnussen, the 2011 and 2013 world champion and silver medallist at the 2012 Olympics in London.
Magnussen was in top form as he clocked a slick time of 47.59sec in the 100m freestyle, and was delighted with his start to the year.
"I'm really happy with tonight," he said.
"I really wanted to put on a good show for the crowd and worked pretty hard at it.
"I was really happy with my race plan, I really put in on the last 25."
The Chinese challenge was lead by Fu Yuanhui, who won the women's 50m backstroke in 27.01sec.
London Olympics dual gold medallist Ye Shiwen easily defended the title she won in Perth last year in the 200m individual medley, one of the events in which she is the current Olympic champion.
Results from the Aquatic Super Series in Perth on Friday night:
1. Australia 3:46.52 (WR), 2. China 3:49.40, 3. Japan 3:53.79
Women's 50m backstroke:
1. Fu Yuanhui (CHN) 27.01, 2. Emily Seebohm (AUS) 28.41, 3. Sayaka Akase (JPN) 28.91
Men's 50m backstroke:
1. Ben Treffers (AUS) 25.14, 2. Kosuke Hagino (JPN) 25.17, 3. Ryosuke Irie (JPN) 25.42
Women's 100m freestyle:
1. Cate Campbell (AUS) 53.08, 2. Bronte Campbell (AUS) 53.98, 3. Karin Prinsloo (RSA) 54.48
Men's 100m freestyle:
1. James Magnussen (AUS) 47.59, 2. Cameron McEvoy (AUS) 48.19, 3. Ning Zetao (CHN) 48.41
Women's 100m breaststroke:
1. Sally Hunter (AUS) 1:08.00, 2. Leiston Pickett (AUS) 1:08.08, 3. Mio Motegi (JPN) 1:08.66
Men's 100m breaststroke:
1. Yasuhiro Koseki (JPN) 59.94, 2. Christian Sprenger (AUS) 1:00.36, 3. Felipe Lima (BRA) 1:01.47
Women's 200m butterfly:
1. Madeline Groves (AUS) 2:07.03, 2. Natsumi Hoshi (JPN) 2.07.83, 3. Ellen Gandy (AUS) 2:08.03
Men's 200m butterfly:
1. Daiya Seto (JPN) 1:54.82, 2. Chad Le Clos (RSA) 1:56.45, 3. Yuki Kobori (JPN) 1:56.85
Women's 400m freestyle:
1. Bronte Barratt (AUS) 4:07.44, 2. Karin Prinsloo (RSA) 4:07.92, 3. Kylie Palmer (AUS) 4:08.67
Men's 400m freestyle:
1. Mack Horton (AUS) 3:47.98, 2. David McKeon (AUS) 3:43.71, 3. Myles Brown (RSA) 3:50.54
Women's 200m individual medley:
1. Ye Shiwen (CHN) 2:10.49, 2. Alicia Coutts (AUS) 2:12.43, 3. Miyu Otsuka (JPN) 2:13.31
Men's 200m individual medley:
1. Kosuke Hagino (JPN) 1:55.90, 2. Daiya Seto 1:58.12 (JPN), 3. Daniel Tranter (AUS) 2:00.27
Women's 200m backstroke:
1. Belinda Hocking (AUS) 2:07.42, 2. Sayaka Akase (JPN) 2:09.88, 3. Emily Seebohm (AUS) 2:10.11
Men's 200m backstroke:
1. Ryosuki Irie (JPN) 1:56.40, 2. Xu Jiayu (CHN) 1:57.21, 3. Matson Lawson (AUS) 1:57.77
Women's 50m butterfly:
1. Alicia Coutts (AUS) 26.35, 2. Lu Ying (CHN) 26.59, 3. Ellen Gandy (AUS) 27.03
Men's 50m butterfly:
1. Nicholas Santos (BRA) 23.61, 2. Ben Treffers (AUS) 23.99, 3. Christopher Wright (AUS) 24.06
Women's 4x200m freestyle relay:
1. Australia 7:55.82, 2. Japan 8.09.48, 3. South Africa 8:16.68
Men's 4x200m freestyle relay:
1. Japan 7:09.81, 2. Australia 7:15.13, 3 China 7:19.17