The Brave Blossoms of Japan overcame the stubborn resistance of inspired hosts Hong Kong to come from behind and win a dramatic series qualifier final 24-14 and book their core team place on all 10 rounds of the HSBC World Rugby Sevens Series 2016-17.
Japan will replace the bottom-ranked of the current core team sides at the end of this season in London - currently Portugal.
Entering the final Japan had not conceded a single point but they struggled for momentum against their most familiar rivals and it needed the calming influence of Lomano Lemeki, who scored a hat trick, to see them home.
Japan built a handy 12-0 lead in the first half thanks to playmaker Lemeki, but Yiu Kan Shing struck back for a converted try for the hosts to cut the lead to just five points at half time.
Alex McQueen's try after the break levelled the scores and Hong Kong led 14-12 with the conversion, but Lote Tuqiri's seven-pointer calmed Japanese nerves before Lemeki's third settled the match late on.
"We've qualified for the Olympics already and we really didn't want to be going to the Olympics without being on the series next season, so we're delighted to have won here, it means a lot," said Lemeki.
Earlier in the semi-finals Hong Kong overcome Germany 17-7 and Japan beat Zimbabwe 22-0.