Kotringo is the stage name of Rieko Miyoshi, a Japanese singer, songwriter, and pianist born in Osaka on July 17, 1978. Her artistic name combines the Japanese words for small bird (kotori) and apple (ringo), reflecting her childhood pet bird and daily apple consumption. She began playing piano at age five and started composing music at age seven. After high school, she attended the Koyo Music School in Kobe before enrolling at Berklee College of Music in 1999, where she majored in jazz composition, arrangement, and piano. She received the piano department's Achievement Award at Berklee and performed as an accompanist for the voice department and as a pianist for a church in Boston. Following her degree completion in 2003, she moved to New York and performed at venues including Detour, Garage, Kaveha's, and St. Nicks.

In the fall of 2005, Kotringo began creating home recordings, and in March 2006, she submitted a demo to Ryuichi Sakamoto's Radio Sakamoto audition corner on J-WAVE, which caught Sakamoto's attention. Her debut single, Konnichiwa, Mata Ashita, produced by Sakamoto, was released in November 2006 as a tie-in song for a Gekkeikan commercial. She has since released numerous albums, including songs in the birdcage (2007), nemurugirl (2008), Sweet Nest (2008), trick & tweet (2009), picnic album 1 and 2 (2010, 2011), La mémoire de mon bandwagon (2012), Tsubame Novelette (2013), birdcore! (2014), Ame no Hakoniwa (2017), and the best album Bird Watcher Kotringo Best (2019).

Kotringo has contributed significantly to anime and animated film soundtracks. She composed the music for the 2016 animated film In This Corner of the World (Kono Sekai no Katasumi ni), directed by Sunao Katabuchi. For this film, she performed the opening song, a cover of Sadashikute Yarikirenai, and created the ending theme Tanpopo as well as the character piece Suzu-san. The original soundtrack was released on November 9, 2016, containing thirty-three tracks including Migite no Uta and Tanpopo. Her connection to director Katabuchi began through his previous film Mai Mai Miracle (Mai Mai Shinko to Sennen no Mahou), for which her song Kodomo no Sekai was used as an ending theme and appeared as a bonus track on her 2009 album trick & tweet.

Additional anime and animation-related credits include the ending theme Chiisana Te no Hira for the television anime Kotarou wa Hitorigurashi, the insert song Harmonia for the animated film Kokoro ga Sakebitagatterunda, and the ending theme Rakuen wo Futari de with Hanaregumi for the animated film Sayonara, Tyranno. She also composed the soundtrack for Gourmet Girl Graffiti (Koufuku Graffiti), released as Edible melodies ~ Gourmet Girl Graffiti Original Soundtrack in 2015, and for the film The Travelling Cat Chronicles (Tabi Neko Ripoto) in 2018.

Her musical identity blends jazz-influenced piano performance with electronic elements and a vocal style described as pure and unadorned. She has cited American rock band Aerosmith and lead singer Steven Tyler as influences. Throughout her career, she has worked under labels including avex, commmons, and Columbia, and has collaborated with artists such as Hanaregumi and the band Kirinji.