After winning the All Japan Figure Skating Championships in January 1983, Osada was sent to the World Championships in Copenhagen in March, 1983. There, she made a series of errors in compulsories, in which she placed a disappointing 24th. In her short program, she missed the triple loop jump in her combination, which only allowed her to pull up to 21st after this segment of the competition. Due to the new rule instituted in the 1982-1983 season (which, incidentally, was abolished after that season), Osada was unable to skate her free program in "Group A," or the main competition consisting of those who placed 15th or above after short program. Instead, she was placed in "Group B" and won the free skate, which resulted in the 3rd-place finish in "Group B"--or 18th overall.
Osada's placement there was noted in ISU's decision not to continue this dual-grouping policy, because her scores in free skating would have placed her 7th in "Group A" in that segment, which would have placed her significantly higher overall. However, she was never given the opportunity to place above 16th in free skate, due to her placement in "Group B." By contrast, many strong compulsory figure skaters who were poor free skaters ended up placing high in the end, because they were guaranteed at least a 15th-place finish in free skating, as long as they placed in the top 15 after short program.
Given the way Osada skated in the 1982-1983 season, many expected her to continue to progress in the world ranks. However, she placed poorly in compulsories at 1983-1984 All Japan Championships, where she finished 4th, costing her the opportunity to compete at the Sarajevo Olympics in 1984. Around this time, Osada experienced a growth spurt, which made her triple jumps less consistent and less dynamic. Although she won a couple of bronze medals at NHK Trophy, she was never able to regain her national title, nor was she able to make the Japanese world or Olympics team. By 1986, she was no longer training seriously, as she shifted her focus to her studies at Hosei University. She retired quietly after the 1989 season.