She graduated from the Osaka College of Music in 1988 and began working in the video game industry by joining Capcom the same year.

She wrote music for several games there, including Final Fight, Street Fighter II, and The King of Dragons.

[3][4] While working for Capcom, Shimomura contributed to the soundtracks of over 16 games, including the successful Street Fighter II, which she composed all but three pieces for.

[1][4] She was a member of the company's in-house band Alph Lyla, which played various Capcom game music, including pieces written by Shimomura.

She performed live with the group on a few occasions, including playing piano during Alph Lyla's appearance at the 1992 Game Music Festival.

While she was working on the score to Super Mario RPG the following year, she was asked to join Noriko Matsueda on the music to the futuristic role-playing game Front Mission.

Although she was overworked doing both scores and it was not the genre that she was interested in, she found herself unable to refuse after her first attempt to do so unexpectedly happened in the presence of the president of Square, Tetsuo Mizuno.

[7][3] Parasite Eve on the PlayStation had the first soundtrack by Shimomura that included a vocal song, as it was the first game she had written for running on a console system that had the sound capability for one.

During the Beware the Forest's Mushrooms performance from Super Mario RPG, Shimomura was joined onstage by fellow composer Yasunori Mitsuda, who played the Irish bouzouki.

[13] She most recently composed and produced the majority of the score for Final Fantasy XV, which she began writing for in 2006, a decade before the game was released.

[18] Legend of Mana's title theme was also performed by the Australian Eminence Symphony Orchestra for its classical gaming music concert A Night in Fantasia 2007.

All songs in each book have been rewritten by Asako Niwa as beginning to intermediate level piano solos, though they are meant to sound as much like the originals as possible.

[28] Shimomura lists Ludwig van Beethoven, Frédéric Chopin, and Maurice Ravel as some of her influences on her personal website.

[4] Despite these influences and her classical training, the diverse musical styles that she has used throughout her career and sometimes in the same soundtrack include "rock, electronica, oriental, ambient, industrial, pop, symphonic, operatic, chiptune, and more".

"[3] Although her influences are mostly classical, she has said that in her opinion her "style has changed dramatically over the years, though the passion for music stays the same.