Ryōko Sawamura attends Hakujō Academy as a classmate, forming a close trio with Shiina Amamiya and Mai Asahina. Her boisterous and hyperactive nature provides a distinct counterpoint to Mai's quieter demeanor, naturally positioning her as a social catalyst within their group. Ryōko favors affectionate nicknames, calling Shiina "Shiina-cchi" and Yūto Ayase "Ayase-cchi," reflecting her informal and approachable personality. She frequently engages classmates through playful physical contact, often meddling in their affairs—particularly romantic matters.

Her involvement significantly centers on Shiina's romantic interest in Yūto Ayase. Alongside Mai, Ryōko actively encourages Shiina's pursuits. She appears unaware or dismissive of the established mutual feelings between Yūto and Haruka Nogizaka, leading to occasional interpersonal friction as she nudges Shiina toward making romantic advances. The meaning of her name derives from "Ryōko" (combining "ryou" 良 for "good/excellent" and "ko" 子 for "child") and "Sawamura" (from "sawa" 澤 meaning "marsh" and "mura" 村 meaning "village").