[3][4][5] Though her early releases presented a conservative, quiet image, she has become a fashion leader among young women, setting trends such as the ero-kakkoii style.

Her grandfather was a Shakuhachi master and her mother was a Koto teacher;[9] she is the older sister of Misono, current solo artist and former lead singer of Day After Tomorrow.

[9] Koda's first semi-biographical book, Koda-shiki ("Koda-style") was officially described as "a story about a girl who was filled with inferiority complex pursuing her way".

The first single was "Lies", followed by "Feel", "Candy", "No Regret", "Ima Sugu Hoshii", "Kamen", "Wind" and "Someday/Boys & Girls".

[48] After Best: Second Session, Koda released "Koi no Tsubomi" which reached number 2 in its debut week with 140,000 copies sold,[49] and eventually topped 1 million downloads.

[50] This was the highest debut week sales for a female artist in 2006, until Ayumi Hamasaki surpassed it with her single "Blue Bird".

[51] Koda reclaimed the title of highest debut week sales for a female artist in 2006 with "4 Hot Wave";[52] which also ranked second behind the KinKi Kids.

[58][59] At the end of 2007, Koda released two singles, "Ai no Uta" and "Last Angel", a collaboration with Korean boy band TVXQ better known as Tohoshinki in Japan.

[61] Having sold more than 7.3 billion yen worth of CDs and DVDs, Koda was again the best-selling artist of the year in Oricon's 2007 year-end rankings.

The single contained "Moon Crying", used as the theme for Asahi Television drama Puzzle, and a collaboration track with The Black Eyed Peas' Fergie[70] Koda again attended Avex's annual summer concert A-Nation '08.

She appeared at all eight shows in Japan and performed with other Avex artists such as Every Little Thing, Ai Otsuka, Namie Amuro, Ayumi Hamasaki, TVXQ, and Maki Goto.

With around 66,000 copies sold in its first week, "Taboo" debuted at the number-one position and became Koda's fifth single to reach the top.

[72] Koda released her forty-second single "Stay with Me" on Christmas Eve, which debuted atop of the chart selling 58,000 copies.

[85] On January 20, 2010, Koda released a new single titled, "Can We Go Back", which is a cover of a bonus track on Kelly Clarkson's 2009 album All I Ever Wanted.

On December 5, 2010, Koda held a concert celebrating her 10th Anniversary named "Fantasia", where she performed a selection of songs from all over her career.

On February 2, 2011, her 49th single "Pop Diva" was released and on February 23, 2011, Koda released "Eternity -Love & Songs- at Billboard Live" an audio DVD of her performance at Billboard Live Tokyo in October 2010, where she performed many songs from her Eternity: Love & Songs cover album.

Koda is featured in the Far East Movement song "Make It Bump", which was only released on the Japanese edition of their album Free Wired.

[92] On August 1, 2012, Koda released a remix album called Beach Mix, which included a new song and a new music video, titled "Whatchu Waitin' On?"

Soon thereafter, Koda embarked on the Bon Voyage Hall Tour, a series of concerts held throughout Japan to help promote the album.

This was followed by a special concert held on December 6 at Studio Coast, called the 'Koda Kumi 15th Anniversary First Class 2nd Limited Live' during which she performed 62 of her songs.

She was the second female artist in forty-years to hold the top two positions on the Oricon Album Charts, after Ayumi Hamasaki who released A BEST 2 in 2007.

On July 20, 2019, Koda released a cover of Ricky Martin's hit "Livin' la Vida Loca" via Avex's official YouTube.

[fn 7] Koda's songwriting credits for other artists include contributing lyrics for Faky's 2019 digital single "New Age".

[133] Singaporean newspaper The New Paper suggested that her sexy image was responsible for her sales—she outsold "reigning J-pop queen" Ayumi Hamasaki in 2006 and 2007.

[148][149] In March 2011, Koda provide aid to the victims of Great East Japan earthquake and tsunami, the Foundation in association with Yahoo!

From January 2020 to October 2021 due to COVID-19 pandemic, Japan issued a "stay-at-home" order and also postponed the Tokyo Olympics at one year time.

[150] On April 19, 2020, Kumi and her husband Kenji03 took part in the song "Be One ~Bokura ni Dekiru Koto~" (僕らにできる事 / What We Can Do), along with various other Japanese artists, including Daichi Miura, Yu Shirota, KEITA, KM-MARKIT and Micro among others.

[153] In the video, Koda and several of her backup dancers perform a dance in their own respective homes, consisting of various yoga poses and lite calisthenics.

[154] In December 2020 amid the third COVID wave, all of songs were recorded in her home studio due to COVID-19 pandemic, which she said gave her more opportunity to work with many Western writers and composers.

[163] At the 2007 Best Hit Kayōsai Koda's "Ai no Uta" earned her the Grand Prix in the pop category, also winning one of the golden awards for the 49th Nihon Record Taishō.