Hanaoka was second to Seiko Nishiuchi at the 1998 Japanese Championships, but she was still selected to compete internationally after clearing a Japanese record of . At the 1998 Asian Games she was seventh and the 1998 Asian Athletics Championships saw her win her first medal for Japan, a bronze with her jump of . After an indoor national record of in February, she made her global senior debut at the 1999 IAAF World Indoor Championships, but finished in last place in the triple jump. She was ninth in the long jump at the 1999 Universiade, but did not get past the qualifiers of the triple jump. She greatly improved her personal best at the national championships that year, setting a national record of . She was also the triple jump champion at the 1999 National Games.