Azusa Matsudaira is the science officer and experimental biologist for the Terrestrial Administration Center (TAC), applying her expertise against Aragami threats. Her background includes previous work at Japan's Science and Technology Agency. At TAC, she focuses on researching Aragami biology and creating specialized biological weapons for field use, rarely participating in direct missions due to her laboratory and development work.

Azusa is divorced, with her son Jun living with his father. Her intense dedication to work contributed to the divorce, straining family relationships. Scheduled visits with Jun occur on the second Sunday of each month, though her workaholic nature sometimes leads her to forget these appointments. This conflict between her scientific career and motherhood fosters self-criticism about her perceived family failures.

In the OVA "Blue Seed Beyond," set two years later, Azusa continues her scientific duties with TAC. The story involves a resurgence of Aragami-like entities created through biotechnology. During a San Francisco mission, she unexpectedly demonstrates high proficiency as a driver, executing precision maneuvers that unsettle her colleagues. Her analytical skills prove vital in investigating the origins of these new biotech threats.

Characterization consistently depicts her as a quietly efficient, dedicated professional who embodies a motherly presence within the TAC team. This role requires significant personal sacrifice, particularly concerning her son. Despite these challenges, her commitment to understanding and countering Aragami threats defines her role throughout her story.