Mitsuki Kimura (born February 5, 2003), known professionally as Koki, is a Japanese model and songwriter. Kimura was born in Tokyo, Japan to actor Takuya Kimura and singer Shizuka Kudô. She had taken lessons in piano and flute and won the Excellence Award at the 23rd Yamano Junior Flute Contest. She attended The British School in Tokyo and is fluent in English. Prior to debuting professionally, Koki had written three songs for her mother's album "Rin" in 2017, as well as for Mika Nakashima. In May 2018, Koki debuted as a model, appearing in the July 2018 issue of Elle Japon. Koki has also appeared on covers for fashion magazines such as Numéro Tokyo, Grazia China, and Nylon Japan, and Vivi. In August 2018, she became the Japanese and youngest ambassador for the luxury brand Bvlgari. In October 2018, Koki appeared in her first commercial, endorsing products from Otsuka Pharmaceutical. In 2019, Koki appeared as a featured artist on Daichi Miura's song, "Katatsumi". Koki also wrote the song. She made her runway debut at the 2019 Paris Fashion Week, representing Chanel.