Dina Asher-Smith started her bid to become the first British woman to win an Olympic individual sprint gold with routine progress from the 100m heats.
Asher-Smith finished behind American Teahna Daniels but reached the semi-finals with a run of 11.07 seconds, reports the BBC.
Team-mates Daryll Neita and Asha Philip also finished second in their heats to qualify for Saturday’s semi-finals.
In the women’s 800m, British trio Jemma Reekie, Keely Hodgkinson and Alex Bell safely reached the semi-finals.
High jumper Tom Gale reached the men’s final with a season’s best of 2.28m.
The women’s 100m has been billed as the biggest draw of Tokyo 2020.
Asher-Smith, 25, is the fastest British woman in history, reigning world champion at 200m, a four-time European champion and an Olympic bronze medallist from the 4x100m relay in Rio.
But she is up against Jamaican duo Shelly-Ann Fraser-Pryce and Elaine Thompson-Herah, who between them have won the past three Olympic 100m titles.
Fraser-Pryce, 34 – the 2008 and 2012 champion – ran a time of 10.63 seconds at a national trials warm-up event in June to become the fastest woman alive and set the bar going into the Games.
Thompson-Herah, 29, will be looking to retain her 2016 title.
Then there is Nigeria’s Blessing Okagbare, who ran her fastest time since 2018 with 10.89secs on July 6.
Asher-Smith went through as the 11th fastest in the heats, as Thompson-Herah (10:82), Fraser-Pryce (10:84) and Okagbare (11:05) ran quicker.
Asher-Smith will run in the first 100m semi-final at 11:15 BST (19:15 local time) on Saturday, with Philip in the second at 11:23 BST and Neita in the third at 11:31 BST.
“It felt good to be out here and to finally get going, and it’s just great to finally get my Olympics under way,” said the Briton, whose season’s best in the 100m is 10.91.
“I was just thinking about making it through to the next round safely, at the same time as knowing I’ve got another level to give.
“I am really happy. And I do have another level – of course I do, it’s an Olympics.”
In the 800m heats, Reekie, 23, was one of only two athletes to run under two minutes, while 19-year-old British champion Hodgkinson and Bell also went through.