おねがいマイメロディ
At the age of 12, Koshimizu joined Theater Company Wakakusa. In the second year of junior high school, she was over 160cm tall and was troubled by the fact that she could not get roles as a child actor. Influenced by her senior in the troupe, Mayumi Iizuka, she began to aspire to become a voice actor. In 2003, she passed an audition for "Ashita no Nadja" and made her voice acting debut as the lead Nadja Applefield. She continued her career with roles in "School Rumble" (as Tenma Tsukamoto), "Onegai My Melody" (as Miki Sakurazuka), and "Eureka Seven" (as Anemone).