Ryōko Sawamura attends Hakujō Academy alongside classmates Yūto Ayase and Haruka Nogizaka. She shares a close friendship with Shiina Amamiya and Mai Asahina, often appearing with them in school and social contexts. Her personality presents a strong contrast to Mai's reserved nature, marked instead by boisterous and hyperactive traits. Ryōko frequently uses affectionate nicknames, calling Shiina "Shiina-cchi" and Yūto "Ayase-cchi."

She actively observes and involves herself in the romantic lives of her peers, particularly noticing Shiina's feelings for Yūto. Alongside Mai, Ryōko encourages Shiina to pursue him, seemingly overlooking or dismissing Yūto's existing mutual romantic connection with Haruka Nogizaka. This involvement contributes to interpersonal tensions within their group.

Ryōko exhibits a mischievous streak, playfully teasing others through physical contact. She engages in this behavior with classmates, often focusing on female peers with more developed physiques, leading to comedic situations. Her name combines the characters for "good, excellent" (良) and "child" (子), while her surname Sawamura means "marsh" (澤) and "town, village" (村).

Her character gains more prominence during the events of "Haruka Nogizaka's Secret: Purezza," the series' second season. Across other official media such as OVAs, movies, or spin-offs, her role remains consistent as part of Shiina and Mai's friend group, with no documented significant evolution or expanded background beyond her school life and friendships.