Scott said both boys were stoked to come away from their first international regatta with medals because they were the younger athletes in their age group, with Sewell being an under-16 paddler and Mills-Nossiter having one more year left as an under-18 paddler.
They both were up against older and more-experienced athletes, but showed gutsy performances to come away with the medals.
Scott also highlighted their performances with their teammates in the K2 500 finals, with Mills-Nossiter and Sewell's teams coming in fourth and fifth respectively.
The race between the two Kiwi boats came down to the wire, and Scott said they were also both close to scoring a podium finish against bigger and more-experienced teams, particularly against the Australians.
Another challenge for the two was having to quickly get used to a change in weather and equipment in Japan.
"They did not have a lot of time to acclimatise to the Japanese summer, the hired boats, the feel of the water or the Japanese cuisine, but they took it all in their stride and enjoyed the cultural experience as well as the racing," Scott said.
He said while the focus of the week was on competition, the boys also enjoyed meeting the other teams and formed a particularly strong camaraderie with the Australian team.