Kaori Kobayashi (小林香織) was born on 20 October 1981 in Fujisawa, Kanagawa Prefecture, and grew up in Tokyo. Her father, Minoru Kobayashi, is a photographer, and her mother taught piano, so the instrument came first. At 13 she joined a school wind band and took up the flute, and in the second year of high school she switched to alto saxophone. In 2000 she entered the jazz course at Senzoku Gakuen College of Music, where she studied jazz saxophone for four years with Bob Zang (ボブ・ザング) and graduated in 2004.

The next year she had a major-label contract. Her debut, Solar, came out on Victor Entertainment's JVC imprint on 23 February 2005 (VICJ-61267): eight tracks produced and arranged by keyboardist Toshiaki Otsubo, with Kobayashi on alto saxophone and flute. Its seventh track, a cover of "Nothing's Gonna Change My Love for You," became her calling card, and she kept re-recording it for years afterward on Golden Best (2009), Precious (2011) and the Spirit (2014) bonus disc. According to her Japanese Wikipedia entry, a 2010 YouTube upload of that song drew very large international viewing numbers and press and television coverage.

Fine (2006) followed, produced by Masanori Sasaji, and in October 2006 JVC issued Kaori Kobayashi Live, a concert film with a band that included the drummer Shuichi "Ponta" Murakami, Sasaji on keyboards, Kiyotsugu Amano on guitar and Kenji Hino on bass. Glow (2007), Shiny (2008) and a run of albums on Victor through 2016 kept her on a roughly annual schedule. Shiny shipped with a documentary of her 2007 concerts in Korea, an early sign of a career that would be built as much abroad as at home: her records have been released in Taiwan, China, Thailand, South Korea, Singapore and Hong Kong, and in 2013 she played the Java Jazz Festival in Jakarta, a set that was released as a bonus disc with Spirit. Her Japanese Wikipedia entry also says she was named "The Most Beautiful Saxophonist in Asia" at an event in Thailand in 2012.

SEVENth (2012) is the album on which Discogs first credits her as producer, and she also produced and arranged Urban Stream (2013). Spirit (2014) was cut with her own working group, the Kaori Kobayashi Band: Mitsuo Kono on bass, Hisayuki Kato on drums, Junko Sugawara and Takuya Tanaka on guitars and Yusuke Miyazaki on keyboards. The 10th-anniversary album Story (2015) revisited her catalogue, and Melody (2016) turned to pop standards, including Eric Clapton's "Tears in Heaven" produced and arranged by the guitarist Shigeru Suzuki and a track with the television personality Sakana-kun.

In 2018 she moved to King Records. The first album there, Be myself! (26 September 2018, KICJ 809), was used as the official background music for the 2018 FIA World Endurance Championship round at Fuji. Now and Forever (10 February 2021, KICJ-90846) marked her 15th anniversary: thirteen new recordings, with Kobayashi playing tenor and soprano saxophone and flute as well as alto, a guest turn from Shigeru Suzuki and his band Huckleback on two tracks, and the vocalist Sian Kelly on the closer. Intersection (10 July 2024, KICJ 871) is her sixteenth album, nine originals with a working quartet of Kento Ohgiya on keyboards and piano, Yoshio Fujita on guitar, Kenta Hamasaki on bass and Nozomu Kitamura on drums. Her father, Minoru Kobayashi, is credited as its executive producer and photographer.

Away from her own records she has provided live support for Yumi Matsutoya, Shigeru Izumiya, Yukihide Takekawa and Shigeru Suzuki, and she is on the Skye releases of 2021 and 2024. She was a lecturer in the jazz course at Senzoku Gakuen, her alma mater, from 2012, and hosted the radio programme Jazz in Tokyo on TOKYO FM from 2006 to 2009. On 30 July 2026 she was the guest saxophonist at singer Ruby Pan's concert in Kaohsiung during the Weiwuying Jazz Week. She turns 45 on 20 October 2026.

Kobayashi plays in the fusion and smooth-jazz idiom, with a clear alto tone and a melody-first approach. In a 2021 interview she contrasted her own priorities with the technical display often associated with fusion saxophone, saying she wanted melody to lead, and described her thirties as the period in which she began producing herself and aiming for saxophone music that does not fit neatly into either jazz or fusion. The Discogs catalogue reflects that spread: nearly every release is tagged jazz, and several also carry funk, soul, pop or rock tags.

The material falls into three streams. The originals, from Solar and Glow through Urban Stream and Intersection, are groove-driven fusion with a rhythm section and keyboards behind a lead alto. Luv Sax (2009) is a set of Japanese pop songs, and Melody (2016) covers Western pop and soul material by Taylor Swift, Alicia Keys, Boz Scaggs, Daryl Hall and John Oates, the Diane Warren ballad "I Don't Want to Miss a Thing" and Beethoven's "Joyful, Joyful" among others. Now and Forever adds hip-hop-leaning tracks and city pop, which she described as an album that can be looked at from every side, like a circular stage.

Her formal jazz credentials sit alongside the pop-leaning output: a Senzoku jazz degree, a teaching post in the same department, a jazz radio show and festival appearances including Java Jazz. This profile treats her as a jazz-fusion artist who works comfortably in pop repertoire, rather than a pop artist who plays saxophone.