10 men's and 12 women's team will contest the Final Repechage event in Monaco on 19-20 June, where one men's and two women's teams will seal the final spots in the main draw.
The men's draw is split into two pools of five, with World Series core teams Samoa and Ireland in Pool A, alongside Tonga, Zimbabwe and Mexico.
Top seeds France are headline Pool B, alongside Hong Kong, Chile, Uganda and Jamaica.
The women's draw is made up of three pools of four teams, with Samoa, Russia, Argentina and Mexico in Pool A.
Papua New Guinea is the top-ranked country in Pool B, ahead of Kazakhstan, Jamaica and Tunisia, with 2016 Olympic representatives France and Colombia joined by Hong Kong and Madagascar in Pool C.
The top two men's teams from each pool will advance to the semi finals, with the overall winner confirming their Olympic berth in July.
Samoa are seeking redemption after conceding a try on the full-time siren against Spain in the final of the 2016 Olympic men's repechage.
In the women's draw, the top two teams in each pool plus the two best third-placed teams will advance to the quarter finals.
The top two teams will secure their tickets to the Tokyo Games.
World Rugby Vice-Chairman Bernard Laporte said the governing body "will now work closely with teams involved in the final qualification event to ensure they all arrive with the best-possible preparation in Monaco in June.
"Together with the Monegasque Rugby Union, we will continue to focus on delivering a safe, secure and thrilling event that puts the welfare of everyone involved at the centre of our operations."
World Rugby is investing US$4 million into Olympic qualified unions' sevens programmes and towards the costs of hosting a number of high-performance preparation events.
The Olympic men's rugby sevens competition will take place from 26-28 July, with the women's tournament following on the 29-31 July at Tokyo Stadium.