It was Uta's first world title, coming just weeks after her 18th birthday, as Hifumi - three years older - successfully defended his crown.
Thoughts immediately turned to the Tokyo 2020 Olympics. Could they do the same there?
After a delay of a year, and Hifumi's victory in a one-off qualification bout that stopped the nation, they had their chance to make history on 25 July 2021.
Incredibly they did it, becoming the first siblings to strike Olympic gold on the same day in an individual sport.
Uta's gold came first as she beat France's Amandine Buchard in an epic women's -52kg final. Minutes later, Hifumi prevailed in the men's -66kg gold medal match against Vazha Margvelashvili of Georgia.
"This has turned out to be the greatest day ever. I don’t think we, as brother and sister, could shine any brighter on this stage of the Tokyo Olympics." - ABE HIFUMI
The start of the dream
Judo spots for the home nation were always going to be fiercely contested.
At the start of March 2020, Abe Uta was named to the team by virtue of her being the two-time reigning world champion at -52kg.
For brother Hifumi, the path was less clear.
After winning the world titles in 2017 and 2018, he only took bronze in 2019 in Tokyo after losing his semi-final to compatriot MARUYAMA Joshiro.
Maruyama went on to take gold, and the All-Japan Judo Federation said April's national championships would decide who would get the Olympic berth.
Of course, in March 2020 came the postponement of Tokyo 2020 due to the Covid pandemic, with those nationals being cancelled.
The federation then organised a single bout between Abe and Maruyama on 13 December, inside the hallowed Kodokan - the birthplace of judo - with the winner going to the Games.
Japan came to a standstill for the contest which, given both men's reputations, would probably also serve as a gold medal decider.
It was truly an epic encounter with Abe emerging victorious thanks to an ouchi gari leg sweep throw for waza-ari 20 minutes into golden score, much to the delight of sister Uta watching in the arena.
Abe Hifumi had clinched the 14th and final spot in the Japanese national team at Tokyo 2020.
He said afterwards, "A lot of emotions flowed through me over the last several days but, today, I just had to go out there and do it. It was do or die. I had the will and never doubted myself for a moment throughout the match.
"Now I can officially say I'm aiming for a gold medal with my sister at the Olympics. As her bigger brother, I can't afford to lose."
In their own words
ABE Hifumi on Uta
Interview with Kyodo, after 2018 World Championship win.
"My target, more than winning consecutive titles, was for us to win as brother and sister. Once my younger sister won, I went into my final with even more resolve to win."
ABE Uta on Hifumi
Interview with Tokyo 2020.
"I couldn’t have made it this far without my older brother. It’s impossible to know if I would have even started learning judo without him."
The Abes' road to the top
Abe Hifumi took up judo aged six after watching a match on television.
He enjoyed success from an early age and won Youth Olympic gold at Nanjing 2014.
Later that year, while still 17, he won the Tokyo Grand Slam to become the youngest Grand Slam winner in men's judo.
Meanwhile, sister Uta started judo aged five and said she “fell in love with the sport from the first day”.
At 16, she became the youngest-ever winner on the IJF World Tour at the 2017 Dusseldorf Grand Prix.
That year, she also won the world junior title in Zagreb, and won December's Tokyo Grand Slam with Hifumi also victorious.
They have since repeated their podium-topping exploits - together - at the 2018 World Championships, the 2020 Dusseldorf Grand Slam, and now the biggest event of them all.
But this is far from the end of the story with both siblings young enough to compete at Paris 2024 and, certainly in the case of Uta, Los Angeles 2028.
As Japan men's head coach INOUE Kosei, a gold medallist himself from Sydney 2000, said, "Together, they have written their own chapter in history. I think we’re witnessing the birth of two new stars in judo right before our eyes."
"I’m counting on them to lead the way for all of judo and I expect a lot from them." - INOUE KOSEI