Higashino Miki grew up listening to classical music since childhood. She started to learn piano and first began written short pieces while still in kindergarten. While an elementary school student, she attended a composition school, learning the music of such composers as Chopin and Beethoven. She also attended a mission school for 6 years, and the church music learned there would be one of the foundational inspirations for her music. She also formed a band in junior high school and wrote many original pieces.
After entering Osaka University's music composition department, Higashino participated in the Yamaha Popular Song Contest where she advanced to the semi-finals. She also started working part-time at Konami and started working on Gradius and Salamander. At university, Higashino majored in composition and took a synthesizer class to learn about the Moog IIIc synthesizer.
Konami offered her a role after graduation but Higashino declined and joined Recruit, a human resources company instead. She would later rejoin Konami as a mid-career recruitment. At Konami she was the lead composer for Gradius III and Contra III: The Alien Wars. As a key member of Konami Kukeiha Club, she worked with many soundtracks for different Konami games, including Vandal Hearts.
Following the success of the soundtrack for Suikoden, for Suikoden II, Higashino Miki was given to opportunity to write the full score and to record the performance of a European orchestra for the soundtrack. Due to her background, Highshino was one of the few game music composers who could write full orchestra music. She did not work on the Suikoden III soundtrack, in part because she had left Konami on maternity leave.
Since then, Higashino Miki has worked as a freelance music composer, mostly notable for Murayama Yoshitaka's game 10,000 Bullets, in 2005. As of 2020, she is stated to be officially retired.