World record holder and defending Olympic champion Adam Peaty topped the timesheets to ease through to the semi-finals of the 100m breaststroke.
Peaty, 26, who is aiming to become the first British swimmer to retain an Olympic title, recorded a time of 57.56 seconds at the Tokyo Aquatics Centre.
Arno Kamminga of the Netherlands, one of Peaty’s biggest rivals for gold, was only 0.24 seconds slower in second.
Fellow Briton James Wilby also qualified in sixth place.
The semi-finals take place on Sunday morning (03:33 BST).
“It was really weird with no crowd, really weird,” said Peaty. “It doesn’t feel like an Olympics. It’s not the same. Of course it’s not. But obviously when you go back to the athletes’ village, that’s when it does.
“We were very delayed here. It’s very hot. But that’s the psychological things we need to adapt to. I had no idea how it was going to feel out there. I’m glad the cobwebs are out now.
“Heats are heats. I always have cobwebs – it’s pretty much the exact same time I did in Rio – and I always build on that. We will just see where we go from here.”
American Michael Andrew, 22, finished third, but his time of 58.62 was nearly a second behind the top two, which suggests Peaty and Kamminga will be going head-to-head for the gold medal in Monday’s final.
Peaty’s qualifying time is the eighth fastest time in history and he was also responsible for the other seven, with his world-record time of 56.88secs set in South Korea in 2019.
Kamminga, 25, is the only man other than Peaty to swim the 100m breaststroke below 58 seconds, with his qualifying time of 57.80secs, a new Dutch record.
Wilby, a 2019 World Championship silver medallist, finished second behind Andrew in his heat but the 27-year-old was comfortably among the 16 fastest finishers to qualify.
Elsewhere, Great Britain’s women comfortably made it through to the final of the 4x100m freestyle relay.
The British quartet of Lucy Hope, Anna Hopkin, Abbie Wood and Freya Anderson won their heat ahead of the United States to qualify in fourth place overall with a time of 3:34.03.
GB’s Max Litchfield qualified for the final of the men’s 400m individual medley in eighth place – only three-tenths of a second ahead of world champion Daiyo Seto, who had been tipped to be Japan’s best hope for gold in the pool.
Aimee Willmott booked her place in the final of the women’s 400m individual medley, qualifying fifth fastest in a time of 4:35.28.
However, there was disappointment for Brodie Williams in the men’s 400m individual medley, Harriet Jones in the women’s 100m butterfly and Olympic debutant Kieran Bird in the men’s 400m freestyle, with all three athletes failing to qualify from their heats.