Daria Bilodid won her second International Judo Federation (IJF) World Championships gold medal by the age of 18 after defeating Funa Tonaki in a repeat of their under-48 kilograms final from 12 months ago.
Ukrainian judoka Bilodid became the youngest ever world champion in Baku in 2018 when she defeated Tonaki, and the pair were seeded as the top two here in Tokyo.
They fought their way through for a rematch at the Nippon Budokan on day one of the Championship in the 2020 Olympic host city.
In an evenly matched contest, Bilodid had to work very hard to avoid being turned onto her back during an early grapple on the tatami, with Tonaki fired up by her home crowd and advancing on the front foot as she looked for the world crown she last won in 2017.
However, Bilodid reversed the momentum with a waza-ari with 90 seconds to go with a fine koshi-waza hip throw, and although Tonaki battled like a woman possessed, she could not deny the teenager a historic second gold.
"This year it was really more difficult than last year, as the Championship was in Japan so I felt a lot of pressure, and also Tonaki prepared all this year and is very strong, but I'm happy I did it," said Bilodid after her victory.
"It was very difficult with my waza-ari to stay strong for the rest of the match, there was a lot of pressure.
"This was my first time fighting in Japan, and was really nice as judo is very popular here, a lot of fans who really understand everything."
Bronze went to third seed Urantsetseg Munkhbat of Mongolia and fifth ranked Distria Krasnaqi of Kosovo.
The first men's gold medal of the Championships went to Georgia's Lukhumi Chkhvimiani in the under-60kg, who added world victory to his European Games triumph earlier this summer.
As the world number nine, Chkhvimiani was unseeded going into this competition, but as many of the top seeds fell away he produced some excellent judo before defeating seventh seed Sharafuddin Lutfillaev of Uzbekistan in the final with two spectacular waza-ari in the final minute.
"Right now I can't say something special, but this is the dream of my life, to get gold in the motherland of judo," Chkhvimiani said after his victory.
"When I was preparing I thought any medal would be perfect, but imagine, I am world champion, my dream comes true in this special arena, in this special atmosphere.
"Thank you to all my supporters, I am extremely happy.
"My coaches did a great job preparing me, but you also need some luck in this situation, and you have to create your own luck too.
"This was my day, I created my victory."
The bronze medals went to Yeldos Smetov of Kazakhstan and Ryuju Nagayama from Japan.
Earlier, three of the top four men's seeds failed to make it to the semi-finals, including defending world champion Naohisa Takato.
Japanese favourite Takato, the champion in 2017 and 2018, was stunned in the quarter-final by Lutfillaev, and missed out on a medal altogether after losing to fourth seed Nagayama having fought through the repechage.
World number one Robert Mshvidobadze of Russia lost to Yung Wei Wang of Chinese Taipei after picking up three shido penalties, while number three seed Amiran Papinashvili from Georgia was another early casualty as he fell to Gusman Kyrgyzbayev of Kazakhstan by a waza-ari.
By contrast, four of the top five seeds in the women's competition reached the semi-finals, with Rio 2016 champion and fourth seed Paula Pareto of Argentina the only judoka to miss out.
Competition continues tomorrow with the men's under-66kg and the women's under-52kg, with insidethegames providing Live Blog coverage of the whole Championships.