She competed for Japan at the 1984 Summer Olympics in Los Angeles, California, although she failed to finish the race.

Masuda set her personal best in the classic distance (2:30:30) in 1983.

She rose to prominence with a gold medal on the track over 3000 metres at the 1981 Asian Athletics Championships and by winning the inaugural 20 km women's race at the Sapporo Half Marathon event.

Her 2:30:30 at age 19 in that race was the World Junior Record.

This biographical article relating to Japanese athletics is a stub.