Imai broke the Japanese indoor record for the high jump in February 1998, winning in Beijing with a clearance of . She edged her rival Yoko Ota to the high jump gold medal at the 1998 Asian Athletics Championships, setting a personal best and championship record of in the process. She jumped one centimetre lower at the 1998 IAAF World Cup to take fifth place for the Asian team. She was over the 1.90 m mark again at the Japanese Championships and defeated Ota to win her second national title. However, in December at the 1998 Asian Games it was Ota who topped the podium while Imai finished in joint fourth place, missing the bronze medal on countback.