The 28-year-old ran solo to the line for 10 kilometres after excellent swim and bike legs in the Japanese city.

After finishing second at the opening race of this season in Abu Dhabi in March, Coldwell's victory has put her top of the overall women's standings.

She ended in 1 hour 53min 32sec as Mexico's Rosa Maria Tapia Vidal claimed her first podium with silver in 1:53:49.

Taylor Knibb of the United States won bronze in 1:54:02.

China's Yifan Yang was a surprising leader out of the water but she was dropped by an eight-strong lead group on the bike.

Coldwell and American Taylor Spivey were the first to the final changeover and the British triathlete kicked on, taking a glimpse behind and then not having any company for the remainder of the run.

She now leads the standings with 1693.75 points after her team-mate Beth Potter, the Abu Dhabi winner, did not race in Yokohama.

Spivey is second on 1433.17 and Vidal has moved into third on 1157.91.

"I'll try not to cry, it's like a dream," said Coldwell.

"I can't really believe it. 

"We had a really good block of training in Australia before Abu Dhabi and raced Abu Dhabi off the back of that. 

"Now I just came here and tried to put the same processes in place. 

"I am literally lost for words and this doesn't happen very much.

"This year for us is all about Olympic selection and it's tough being from GB, we have such a strong roster of girls. 

"Hopefully this is another step forward to try and make that team."

In the men's race, Tokyo 2020 bronze medallist Hayden Wilde of New Zealand came out on top in the wet conditions.

Wilde positioned himself at the front of the bike leg and left defending world champion Léo Bergere of France behind on the run as he triumphed in 1:42:13.

A tight sprint finish behind him saw Matthew Hauser of Australia gain silver in 1:42:17 and Vasco Vilaca of Portugal pinch bronze in 1:42:18, as Bergere faded to fifth.

"I was really going for this one," said Wilde. 

"In Abu Dhabi, I had a mechanical and I didn't get to show what I had, so today I wanted to come out here and give it some."

In the overall standings, Vilaca has claimed the lead with 1549.38 points after he finished second in Abu Dhabi.

Britain's Alex Yee, who won the first leg, was missing in Yokohama.

Dorian Coninx of France is second overall on 1340.52 and Bergere is third on 1239.98.

The circuit now moves to Cagliari on Italian island Sardinia on May 27 and 28.