From elementary school, Kotoko believed her career would be influenced by her voice and tried to involve herself in as many auditions as possible. In addition to regular education she attended courses at the music school Haura where she polished her musical talents.
Kotoko became a professional singer in 2000. Her first successful audition was with I've Sound, a team of producers using the talents of various female vocalists for their productions—best recognized for their many dating sim and eroge game soundtracks. Since then, she has performed opening and ending themes for a few anime and has gained significant recognition from her two I've Sound-related album releases. Her second album, Garasu no Kaze, released in June 2005 has been praised within multiple online communities. On October 13, 2005, she released her fourth maxi single, which featured a song from her Garasu no Kaze(硝子の靡風?) album, "421: A Will" and its B-side song "Shūsō" (秋爽,The Refreshing Autumn Breeze?), which is featured in her third album, Uzu-Maki.
Although not listed on her official profiles, Kotoko has actually released seven albums. Her first album was Sora o Tobetara(空を飛べたら,I Can Fly?), which was released in 2000. Many of the tracks on this album were later re-recorded for her first I've Sound album, Hane(羽 -hane-,Feather?), which was attributed as her first album. Her first I've Sound CD appearance was on the CD "Dear Feeling" sold in Comiket 59, together with singer Aki. She then appeared on the album Disintegration, a collection of various songs from I've Sound's singers.