Ryoko Takeuchi is the second-in-command at the Terrestrial Administration Center (TAC), transferring from the Tokyo Metropolitan Police Department. Born in Hokkaido, her police training honed her into a skilled sharpshooter who frequently utilizes standard-issue and modified firearms against Aragami threats.

She dedicates herself intensely to TAC's mission, proactively leading field operations and immersing herself in combat. A profound sense of responsibility for Kaede Fujimiya's death drives her actions, fueling a protective stance toward Momiji Fujimiya and pushing her to rigorous efforts to prevent similar tragedies. Despite her typically composed demeanor, she consistently offers emotional support to Momiji during distress.

Her professional commitment intersects with personal feelings; she deeply admires and develops romantic feelings for TAC director Daitetsu Kunikida. This dynamic is complicated by Kunikida's reluctance stemming from their age difference, though they maintain effective teamwork. Ryoko struggles to openly express her emotions despite her persistence in the relationship.

Within TAC, she maintains positive rapport except for frequent conflicts with colleague Sugishita, whose persistent advances irritate her. Her blood type is AB, and her zodiac sign is Leo.