Jun, who took bronze at the most recent World Championships in 2019, finished with 1,457 points.

He shared the podium with Hungary’s 35-year-old Robert Kasza, world silver medallist in 2017, who took silver after finishing just two points behind, and Ilya Palazkov of Belarus, who earned bronze with a total of 1,451.

"It's an incredible day," Jun told the UIPM website.

"For a long time I missed the competitions and it's fantastic to be back.

"In the semi-final it was snowing and my body struggled, but today was nice weather and nice conditions and I'm very happy. 

"I'm looking forward to the Tokyo Olympic Games."

Reflecting on his failure to qualify for the final at the home World Cup held last month, Kasza said: "Actually I'm very glad because it was very tough for me in Budapest in the last competition.

"For the first time in my life I didn't make the final, so my soul was broken, my heart was broken.

"Somehow I fixed it very quickly, and I'm very proud of my team and my family and everyone who supported me.

"It was quite a good day and all the pieces of the puzzle came together.

"I'm looking forward to the next competition and I'm so motivated."

Palazkov commented: "It has been a long, long road these past two years, especially last year with COVID, and I'm so happy to start competitions again.

"It's very beautiful."

Jun had put himself in a podium position after the opening swimming discipline, where he finished second, six points behind Britain’s 2019 world silver medallist Joseph Choong, who amassed 312 points.

But the picture changed after the fencing, with Palazkov taking over the lead with 549 from Kasza on 540 and Jun dropping to bronze position on 533.

The two leaders maintained their position after the riding, with Palazkov advancing into the concluding laser-run top of the field with 842 ahead of Kasza on 833.

But after he finished 15th, the South Korean's position on the podium was usurped by Britain’s Thomas Toolis, who took over third place on 827.

However, 10th place in the concluding laser-run in a time of 11min 9.80sec was enough to give Jun victory as Palazkov dropped to third after finishing 23rd and Kazsa moved up to silver after finishing 15th.

The event, the first of two back-to-back World Cups to be held in Sofia in a competition calendar condensed by the UIPM because of the coronavirus pandemic, is due to conclude with the mixed relay tomorrow.

With so many Tokyo 2020 qualification points on offer a huge field of 199 athletes from 40 countries has gathered in Bulgaria for the two competitions.