Seiko made her debut as a Japanese POP star in 1980, at the age of 18.
Seiko has a total of 25 number-one singles and held the record for a female artist with most #1 singles until Hamasaki Ayumi broke that record in March 2006. Still, Seiko holds the record for the most consecutive singles to reach number-one (24).
Seiko was the inspiration of many up-and-coming Japanese idols throughout the 1980's. Sakai Noriko idolized Seiko more than any other idol. Noriko made her debut in 1986, using the Sakai Noriko name as her stage name. It has been mentioned in several sources that she chose the name "Noriko" after her favorite Japanese idol. Seiko is also a stage name, where her real name is Kamachi Noriko. Noriko also signed on with Sun Music in 1986, the exact same recording company as Seiko.
Most Japanese idols choose to marry at the end of their careers, not during. The marriage between Seiko and actor Kanda Masaki was one of the largest entertainment news stories of the 1980's. Not only did Seiko marry someone during the peek of her career, but the wedding ceremony itself cost about 200-million yen (or US$2.0 million).
In a CNN (Atlanta, GA) news piece aired during the late 1980's, they coined Seiko as the "Japanese Madonna". Throughout most of the late 1980's, much of Seiko's music resembled the works of the POP diva from the United States. Seiko has also mentioned in many interviews that Madonna was her role model.