Andy Murray faces a tough start to the defence of his Olympic tennis title after being drawn against ninth seed Felix Auger-Aliassime.
Murray is the only tennis player to win back-to-back singles gold medals having triumphed in London and Rio but his hopes of making it three in a row have been severely hampered by physical struggles.
He won consecutive matches at a grand slam for the first time in four years at Wimbledon before being comprehensively beaten by Auger-Aliassime's Canadian counterpart Denis Shapovalov and then giving a downbeat assessment of his career prospects.
Twenty-year-old Auger-Aliassime, meanwhile, headed to Tokyo on a high after a strong grass court season that culminated in a first grand slam quarter-final appearance at SW19, while he easily defeated Murray at the US Open last year.
Debutant Liam Broady, a very late entrant to the field after numerous withdrawals, will take on Argentina's Francisco Cerundolo while Heather Watson opens against Anna-Lena Friedsam of Germany.
Dan Evans and Johanna Konta, who would have represented Britain's best hopes of singles medals, were both forced to withdraw ahead of travelling after testing positive for coronavirus.
Plenty of star names have remained at home, including Roger Federer, Rafael Nadal and Serena Williams, but Wimbledon champions Novak Djokovic and Ashleigh Barty are both in Japan along with Naomi Osaka, who will play her first match since withdrawing from the French Open.
Djokovic, who is bidding to become the first man in history to win a Golden Slam of all four grand slam titles and Olympic singles gold in the same year, will take on Bolivia's Hugo Dellien first up, with Daniil Medvedev, Stefanos Tsitsipas and Alexander Zverev the other top-four seeds.
Barty faces a tricky opener against Spain's Sara Sorribes Tormo while Osaka, who would have been the subject of intense attention as one of the faces of the Games even before the furore that blew up over her decision not to fulfil her media duties in Paris, takes on Zheng Saisai of China.
Osaka has not played a match since opening up about her mental health struggles and pulling out after one round in Roland Garros, with the 23-year-old deciding not to play at Wimbledon.
Britain's best hope of a medal may come in doubles, although Andy Murray and Joe Salisbury were given a tough draw against French second seeds Pierre-Hugues Herbert and Nicolas Mahut.
Jamie Murray and Neal Skupski will take on Argentinian duo Andres Molteni and Horacio Zeballos.
Entries for the mixed doubles will be announced on Tuesday.