She was one of the vocalists of the FictionJunction project started by Yuki Kajiura, and is a core member of the vocal group Kalafina.

"Kaze no Machi e" (風の街へ, "To the City of Wind") was used as an insert song in episodes 19 and 21 of the anime show Tsubasa: Reservoir Chronicle, and "Nohara" (野原, "Field") was the B-side for the FictionJunction single "Toki no Mukou, Maboroshi no Sora".

In 2007, she and FictionJunction member Wakana joined Kajiura's vocal project Kalafina, releasing the song "Oblivious".

[6] She also rejoined FictionJunction for Kajiura's concert performance of tracks from the Princess Principal anime television series.

[10][11][12] Her solo concert KEIKO Live K002 ** Lantana * Saita yo to promote the album is scheduled for December 16 at Zepp Tokyo and includes a livestreaming of the event.