Eriko Yoshizawa is a dedicated officer in the Tokyo Metropolitan Police Department's special investigations unit, serving as Ken Kanzaki's direct partner and reporting to Chief Jōgasaki. After a near-fatal attack on Jun Zaizen involving Ken, Ryō Aguri, and Gō Gōda, she grieves Ken's apparent death until his surprising return as part of the covert Metal Jack unit. Her police duties involve standard investigations and responding to crimes, frequently placing her in perilous situations where she exhibits a professional yet sometimes reckless approach to law enforcement.

Throughout these events, she forms a romantic relationship with Gō Gōda, the professional wrestler resurrected as Blue Jack. This relationship deepens despite Gō's dual existence as a Metal Jack cyborg and his role as the team's comic relief. Her connection to Gō marks a key personal evolution, distinct from her initial professional partnership with Ken.

Her personality combines a professional, no-nonsense demeanor during police work with a capacity for protectiveness towards her Metal Jack colleagues. She also demonstrates compassion, particularly concerning animals, and owns a pet dog named Spunky.