Hailing from Fukuoka, Leo Ieiri made a definitive decision to pursue a career in music at the age of 15 when she completed her explosive debut single "Sabrina", showcasing the turmoil of adolescence. She made her major debut in February 2012 while attending a high school in Tokyo, with her first album "LEO" reaching #2 on the Oricon charts for two consecutive weeks. Ieiri received numerous awards, including the Best New Artist at the 54th Japan Record Awards, and her debut one-man tour sold out immediately in January of the following year. Graduating from high school in spring 2013, she went on to provide theme songs for various dramas and commercials.

In celebration of her 5th debut anniversary in February 2017, Ieiri released her first best album "5th Anniversary Best" and held her first performance at Nippon Budokan, which was a sold-out success. She continued her success with her first movie tie-in song "Kono Sekai de" for the film "Code Geass: Lelouch of the Re;surrection" in January 2019, followed by a 7th anniversary concert in Osaka. Her latest original album "DUO" was released in April 2019, accompanied by the "Leo Ieiri 7th Live Tour 2019" with a triumphant final show at Makuhari Messe International Exhibition Hall 9-10. Ieiri has since continued to release new music, including her latest single "Sora to Ao" for the TV drama "Uchi no Musume wa, Kareshi ga Dekinai!!" marking her 17th single in 2021, as she enters her 10th year in the music industry.