Kiroro

Kiroro is a Japanese musical group out of Okinawa and is comprised of vocalist Chiharu Tamashiro and piano/keyboard player Ayano Kinjoh. Kiroro first debuted in 1996 as an independent band, and later made their major debut in 1998 with the song “Nagai Aida (長い間)”.

Eventually their song “Best Friend” was put into the very popular drama “Churasan” causing them to sprout even more fans.

Source: http://www.last.fm/music/Kiroro/+wiki