Kodaira is the first Japanese woman to win an Olympic gold medal in speed skating.

At the 2010 Winter Olympics she won a silver medal in the team pursuit event.

At the 2015 World Single Distance Championships, she won the bronze medal in the 500 m event.

Kodaira took the top step also in every single ISU World Cup one in the 2017–18 season ahead of the Olympics.

[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.