After losing the national title to Tamie Motegi in 1978, her breakthrough year came in the 1979 track and field season. She set a championship record of 13.81 seconds to regain her Japanese crown. She was her country's leading hurdles entrant at the 1979 Asian Athletics Championships, held on home turf in Tokyo, and won the gold medal with a championship record of 14.17 seconds, comfortably ahead of China's Dai Jianhua and her compatriot Motegi. A global debut followed at the 1979 IAAF World Cup in Montreal, where she placed eighth as Asia's representative. Akimoto defended her national title in 1980, then again in 1981, improving further to 13.71 seconds. She won another bronze medal at the Pacific Conference Games that year – one of only three Japanese women ton win an individual medal there, alongside high jumperHisayo Fukumitsu and fellow hurdler Yumiko Aoi. She remained unchallenged at continental level, repeating her hurdles victory at the 1981 Asian Athletics Championships in a new championship record of 13.78 seconds ahead of China's Dia. Another appearance for Asia came as a result at the 1981 IAAF World Cup, where she again placed eighth.
Asian Games and third Asian title
Her career peak came at the 1982 Asian Games. Dia of China entered as defending champion but two Japanese women finished ahead of her: Akimoto claimed the gold in a lifetimebest of 13.63 seconds, trailed by Chizuko Akimoto. She then teamed up with Emiko Konishi, Hiromi Isozaki and Junko Yoshida to form the Japanese women's 4×100 metres relay quartet. The team comprised some of the best sprinters of the region: Konishi was the reigning 200 m Asian champion, Isozaki had won a double sprint at the Asian Games, while Yoshida was the reigning 400 m Asian champion. The team won the gold medal in an Asian record of 45.13 seconds. Akimoto's win-streak at national level extended to 1983, meaning she had gone unbeaten in five finals at the event. In her last year of international competition she competed under her married name: Emi Sasaki. She had a third consecutive win at the 1983 Asian Athletics Championships, equalling her time from the Asian Games to set a championship record, despite a strong −2.0 m/s wind. This was almost two tenths of a second faster than runner-up Liu Huajin of China, who would go on to win the title herself two years later. Akimoto was one of three Asian entrants in the women's 100 m hurdles at the inaugural 1983 World Championships in Athletics, alongside her traditional rival Dia and Lin Yueh-Hsiang. With a run of 13.73 seconds in the quarter-finals, Akimoto was the best performer among them, but this left her in eighth and she was eliminated. She made her final contribution to the Japanese record book with a time of 7.19 seconds for the indoor 50 metres hurdles in 1986. This mark remains unbeaten. Following her retirement, she has remained connected with athletics and worked with the Japan Association of Athletics Federations to promote the sport among children.
National titles
Japan Championships in Athletics
*100 m hurdles: 1977, 1979, 1980, 1981, 1982, 1983