The Japanese clinched his fourth successive world title as fellow Olympic gold medallists Sandra Sánchez of Spain, Serbia’s Jovana Preković and Frenchman Steven Da Costa also retained their crowns.

Brazil’s Douglas Brose secured the third world gold of his career at the age of 35, while 37-year-old Gogita Arkania of Georgia also rolled back the years to earn his second.

Azerbaijan's Olympic silver medallist Irina Zaretska and Japan’s Miho Miyahara also returned to the top of the podium at the World Championships, while Egypt’s Youssef Badawy and Ahlam Youssef, Dastonbek Otabolaev of Uzbekistan and Spain's Maria Torres Garcia stood on the first step for the first time.

Kiyuna maintained his unbeaten streak at the World Championships, which stretches back to Bremen in 2014, by seeing off arch-rival Damian Quintero of Spain in the men’s kata final.

In a repeat of the Olympic gold-medal bout and the 2018 world final, Kiyuna scored a huge 28.36 to gain another victory over Quintero, who was forced to settle for silver on 26.66.

Six-time European champion Sánchez was equally dominant, retaining her women’s kata crown after beating Japan's world number six Hikaru Ono.

The Spaniard’s routine was rewarded with 28.46, with Ono taking silver on 27.42.

Da Costa, the first Olympic champion in karate, sealed a second straight men’s under-67 kilograms kumite crown in style as he raced into an eight-point lead over North Macedonia's Emil Pavlov to bring an early end to the final.

Preković successfully defended her title in contrasting fashion, surviving a scare in her under-61kg gold-medal contest against Ukraine’s European Games champion Anita Serogina.

The Serbian, the reigning European, world and Olympic champion, needed a late yuko - a one-point score - to see off a determined Serogina 2-1.

Brose dethroned Angelo Crescenzo in the men’s under-60kg final after landing an early ippon in 3-0 win over the Italian.

Victory handed the Brazilian a first world title since he won the same event in Bremen seven years ago.

Another veteran to enjoy success today was world over-84kg number one Arkania, who had also not won gold at the World Championships since the event in the German city in 2014.

Arkania edged out Italy’s former European champion and world number 20 Simone Marino 3-2 to claim the title.

Zaretska was in ruthless form en route to the women’s under-68kg final but came up against a tough opponent in world number four Silvia Semeraro.

The European champion, who used to represent Ukraine, took a 3-0 lead early on before Semeraro responded with ippon and felt she had won it with a yuko in the dying seconds, but the judges disagreed and Zaretska claimed victory on first-point advantage.

Miyahara was also pushed all the way as she beat world number three Shara Hubrich of Germany by decision after their scrappy women’s under-50kg final had ended level at 0-0.

Torres, ranked sixth in the world, added to Spain’s gold medal tally after she ousted Menna Shaaban Okila of Egypt 5-4 in a thrilling women’s over-68kg encounter.

Okila’s compatriots Badawy and Youssef went one better by securing the men’s under-84kg and women’s under-55kg titles, respectively.

Badawy, 16^th in the world, overcame Chile’s world number 50 Fabian Huaquiman 6-5 in perhaps the most entertaining bout of the day.

Youssef was declared the winner after American Trinity Allen was unable to compete due to an injury she suffered in her semi-final against Jessica Warling of Luxembourg.

Egypt were denied a hat-trick of titles after Uzbekistan's Dastonbek Otabolaev beat Abdalla Mamduh Abdelaziz 4-3 in the men’s under-75kg final.

The Championships, the first to be held in the Middle East, conclude with the team gold-medal bouts tomorrow.

To relive all the day's action, including results of the bronze-medal contests, click here.