Natsumi Tsunoda became the third Japanese woman to win three world judo titles in a row, but Tokyo Olympic gold medalist and four-time world champion Naohisa Takato finished out of the medals on Sunday.
On the opening day of the world championships in Doha, Tsunoda won all five of her matches in the women's 48-kilogram category by ippon, including the final against top-ranked Shirine Boukli of France.
"I'm relieved and simply happy," said the 30-year-old Tsunoda, who took a big step toward next year's Paris Olympics. "I knew how important it was to go all the way here. Without being satisfied with this result, I want to make use of it in the next event."
Tsunoda joined Ryoko Tamura and Noriko Anno in the three-peat club.
Japanese compatriot Wakana Koga, 21, settled for bronze after losing to Boukli in the semifinals and winning a third-place match via the repechage.
In the men's 60-kg category, Takato lost to eventual winner Francisco Garrigos of Spain by ippon in the semifinals and then suffered a foul loss to South Korea's Lee Ha Rim in a match for bronze.
It was the first time that Takato has missed out on a medal in an international event since the world championships in Tokyo in August 2019. In Doha, the 29-year-old was looking to become the only Japanese five-time world champion.
"I feel, once again, that it's difficult to keep winning," Takato said. "Everybody is studying my judo, so things were harder than I expected."