Her parents encouraged Onitsuka to listen to Western music and by the time she was ten, she wrote her first poems, receiving praise from her parents, friends and teachers, who called them 'earnest efforts'. Secretly, however, she knew that just writing 'earnestly' wasn’t enough. From that time onward, she tried to write every day, and by the time she was in junior high school, she began to gain more confidence.

Having been influenced by Alanis Morissette in junior high school days, it was the encounter with Jewel’s music and presence during the high school years that strongly impelled Onitsuka to become a singer-songwriter. With some 70 original compositions and several other auditions under her belt, Onitsuka entered the 1998 Virgin Tokyo Artists Audition, going on to winning Grand Prize. Then only 17, Onitsuka started her career as a professional and moved to Tokyo in spring 1999 after graduating from high school.

February 2000 saw the release of Onitsuka’s debut single "Shine." The following single "Gekkou" was selected the theme song to a TV drama series, gaining nationwide attention to this new artist. While "Gekkou" remained a long-term best-seller, the up-tempo single "Cage" was released in November 2000, followed by the fourth single "Memai/Edge" in February 2001 which was Onitsuka's first love song. The highly anticipated debut album Insomnia was then released in March 2001, immediately topping the Original Confidence album sales charts in the first week of release.

After the release of the first DVD/video Me And My Devil, a collection of her video clips, Onitsuka embarked on the first tour Chihiro Onitsuka Live Tour 2001, fascinating her fans with her irresistible charm and vocal performance. She then appeared at various rock festivals across Japan in summer of 2001, solidifying her status as a performing artist. Her strong presence was imprinted on many rock fans as she was only accompanied by a piano on stage at the festivals full of famous rock bands.

"Infection/Little Beat Rifle", the first single since debut album was released in September. "Infection" conveyed a grand scale and dynamics while "Little Beat Rifle" was of a completely different taste, and the double A-side portrayed the infinite potential of Onitsuka’s.　The release of the first live DVD/video Cradle On My Noise followed in November 2001. Onitsuka’s words and music were then honoured in public as she was awarded The Best Lyrics Award for "Memai" at The Japan Record Award (December 2001) and Rock Album Of The Year for album "Insomnia" at The Japan Gold Disc Award (March 2002).

2001 also saw Onitsuka’s music travel overseas. "Innocence" from her first album Insomnia was used in the soundbed of the TV campaign for Applied Materials based in Silicon Valley. The TV campaign aired on different channels including CNBC and CNN, resulting in many phone calls from the viewers asking who the singer was that they heard on the TV spot. Also, her song "Rasen" was used in the Luc Besson film Wasabi starring Jean Reno and Hirosue Ryoko, further showing the potential that Onitsuka’s music has of penetrating the international market.

In 2002, Onitsuka released her sixth single "Ryuuseigun" in February, followed by the second album This Armor on March 6. This Armor showcases her many different expressions. Then her second live tour Chihiro Onitsuka Live Vibe 2002 took place with great reaction at each venue.

In early September 2003, Onitsuka recorded her October single "Ii Hi Tabidachi, Nishi e," a cover of a 1978 song, to be used as the theme for Japan Railway's "Discover the West" campaign. She recorded this song right before she took a hiatus to have throat surgery.[1]