While Kusumi was in Morning Musume, she provided the voice for Kirari Tsukishima, the main character of the anime series Kirarin Revolution, and portrayed her in real life on Oha Suta.
Kusumi also ventured into acting, appearing in shows such as Woman Prisoner 7 and Doctor-X: Surgeon Michiko Daimon.
Koharu Kusumi was born in Ojimaya, Washima Village in Niigata Prefecture, and grew up in a rural neighborhood.
In 2005, after seeing an audition call for new members for the Japanese idol group Morning Musume in a magazine, Kusumi considered applying after noticing she was eligible based on the minimum age requirements to participate.
[2] She sang "Furusato" during the final audition[2] and was selected for the group as the only seventh generation member, a feat which earned her the nickname "Miracle" from producer Tsunku.
[3] Kusumi also made crossover television and concert appearances as Kirari on Haromoni@ and Oha Suta,[4] leading her to become closely associated with the character.
[3] The success of Kirarin Revolution and Kusumi's real-world appearances as Kirari made her one of the earliest examples of the "idol voice actor" crossover that became popular beginning in the late 2000s.
[5] Throughout the show's run, Kusumi also released music as groups Kira Pika and MilkyWay with other cast members.
[13] In July 2010, she performed with Li Chun, Qian Lin, and Miyabi Natsuyaki at the Shanghai World Expo 2010 under the group name Ex-ceed.
[32] In early 2017 it was announced that Kusumi would be represented by Oscar Promotion, and would have a role as geisha in a drama called "Woman Prisoner 7."
[33] In October 2017, Kusumi appeared in the fifth season of the popular medical drama, Doctor-X as Nurse Haruna Nagamori.