At the 2017 World Single Distance Championships, she became the first Japanese woman to win an individual single distance world title winning the women's 500 m event.[1] She won also silver medal in the 1000 m event at the Championships. At the 2017 World Sprint Championships, she won the women's competition. In the season, she became overall winner of ISU World Cup 500 m cup.
Kodaira took the top step also in every single ISU World Cup one in the 2017–18 season ahead of the Olympics.[2]
She is the current world record holder in the 2×500 metres and the sprint combination,[3] and the former world record holder in the 1000 metres[4] and the team sprint, as well as the current Olympic and Japanese record holder in the 500 metres.[5][6]
At the 2018 Winter Olympics, Kodaira won gold medal in the women's 500 m event and the silver medal in the women's 1000 m event respectively. In the former, she also set an Olympic record and became the first woman to break the 37-second barrier at sea level, as well as the first female Japanese Olympic champion in speed skating.[7] In April 2022, Kodaira announced that she will retire from speed skating in October after a final race at the national single distances championship to be held in her hometown Nagano.[8]