Ryoko Takeuchi, born in Hokkaido, Japan, served as a Tokyo Metropolitan Police officer before joining the Terrestrial Administration Center (TAC). Her law enforcement background provided strong investigative instincts and proficiency with standard police firearms, later expanded through specialized weapons modified against Aragami threats.

Within TAC, she operates as a calm, collected, and dedicated second-in-command under Daitetsu Kunikida, frequently leading field operations. She balances strength with gentleness, offering consistent emotional support to colleagues—especially comforting Momiji during distress—and demonstrates sharp shooting skills.

Ryoko harbors profound guilt over Kaede Kunikida's death, believing her intervention insufficient. This drives her resolve to protect Momiji and prevent similar outcomes, aligning with her strong patriotism and commitment to Japan's safety.

She develops deep romantic feelings for Kunikida, persisting despite his initial reluctance over their fifteen-year age difference. Their professional relationship evolves personally, culminating in marriage by the series' conclusion. While generally amiable with teammates, she exhibits friction with Sugishita due to his persistent romantic advances.

Her blood type is AB, and her zodiac sign is Leo.