She won her first national title at the Japan Championships in Athletics in 1995, topping the podium in the 5000 metres with a time of 15:14.77 minutes,[4] which was a Japanese record for the event.[5] Yashima was chosen to represent Japan in the 5000 m at the 1995 World Championships in Athletics, but she failed to maintain her level of performance and was eliminated in the first round after finishing sixth in a slow, tactical heat.[6]
Yashima also represented her country in ekiden road relays, winning on two occasions: she won her leg at the International Chiba Ekiden in 1994 and finished second in her leg of the 1995 Beijing International Women's Ekiden. She did not compete again at a high level after the 1995 season.[7]