[1] Formerly signed to the Avex Trax label for 22 years, Shimatani started her career as an Enka singer with the release of her debut single "Ōsaka no Onna" (大阪の女, Ōsakan Woman) in 1999, but later decided to get into the dance/pop style for her music.

At the age of seventeen, while still in high school, Shimatani attended "The Japan Audition 1997", where she was chosen as the winner out of around 200,000 people and got a recording contract with the Avex label.

Mainstream success did not come until 2001 with the release of Shimatani's third single, "Papillon", a Japanese version of Janet Jackson's song "Doesn't Really Matter".

In May 2002 she released another cover, this time of "Amairo no Kami no Otome" by the 60's group sounds band Village Singers.

[3] In February 2005, Shimatani released her first concept album, Crossover, which marked a sustained shift her music, from mainstream J-pop to classical-influenced tunes.

Since then her music has been heavily influenced by string instruments and pianos, instead of electric guitars, bass and keyboards, and also started to include some world ethnic elements.

On March 7, 2007, Shimatani released her 6th studio album, Prima Rosa, which peaked at number 16 on the Oricon charts.

For the album she also made a new crossover version of "Amairo no Kami no Otome", which she performed live at that year's Kōhaku.

In July she celebrated her tenth anniversary in music releasing the greatest hits album Best & Covers, and also holding a special live concert in the Itsukushima Shrine.