Kaoru Mori was born on September 18, 1978, in Tokyo, Japan. Before her professional debut, she created self-published dōjinshi under the pen name Fumio Agata as a member of the dōjin circle Lady Maid. Her professional career began when she was scouted by an editor at Enterbrain, leading to her first serialized work.

Mori is the original creator of several notable manga series, many of which are centered on female characters in the 19th century. Her first professional serialization was Emma, which ran in Enterbrain's Comic Beam magazine from 2002 to 2008 and was collected in ten volumes. The manga is a historical romance set in Victorian London, following the relationship between a housemaid named Emma and William Jones, a member of the gentry. Emma received critical acclaim, including an Excellence Prize at the 2005 Japan Media Arts Festival.

The success of the manga led to an anime television adaptation titled Emma: A Victorian Romance. The first season, consisting of 12 episodes, was directed by Tsuneo Kobayashi and produced by Studio Pierrot, airing in 2005. Mori is credited as the original creator for the second season, Emma: A Victorian Romance Second Act, which aired in 2007. This second season was produced by Ajia-do Animation Works and also consisted of 12 episodes, continuing the story of Emma and William.

Prior to Emma, Mori had created Shirley, a manga centered on a young maid, which was first released as a volume in February 2003. This work was revived in 2010 with a two-part continuation called Shirley Madison in the magazine Fellows! (later known as Harta). Her most recent major work is A Bride's Story, which began serialization in Harta magazine in October 2008. The series later transferred to Kadokawa's Aokishi magazine in June 2021. A Bride's Story has also been highly honored, receiving the Prix Intergénérations at the 2012 Angoulême International Comics Festival and winning the seventh annual Manga Taishō Award in 2014.

Mori's artistic identity is defined by a meticulous attention to historical detail, particularly in clothing design, architecture, and background elements. Her works are known for their high level of craftsmanship, often leading to her manga being published in larger, hardbound editions outside Japan to better showcase the intricate artwork. She frequently explores themes of daily life and customs in historical settings, focusing on female protagonists from different cultures, including a maid in Victorian Britain and a bride in 19th-century Turkic Central Asia. Mori is known to be a private individual who is reluctant to show her face during public events or interviews, often depicting herself in unflattering self-portraits as a simple outline with wild hair. Her significance in the manga industry is underscored by her international awards and the unique position her works hold for their detailed, researched, and largely positive portrayals of historical life.