Risa Tomosato is an 18-year-old university student with a slight, porcelain-skinned frame and striking violet eyes, standing 155 cm tall. Her blond hair flows into cascading straight twin tails, accented by curtain bangs parted centrally and spiky strands framing her face. She favors casual ensembles like miniskirts, pleated skirts, patterned thigh-high stockings, and turtleneck tank tops, often accentuated with ribbon-adorned hair ties or belts. Embodying the tsundere archetype, Risa blends sharp-tongued bravado with concealed vulnerability, masking unspoken affection for Ryuichi Moroboshi through brashness and feigned indifference. Her interactions with him oscillate between calculated teasing and poorly veiled jealousy, often prompting visits to his home under the guise of feigned frugality rather than admitting her loneliness as a nearby solo resident. As Kyoko Moroboshi’s younger half-sister and Ryuichi’s stepsibling, Risa navigates domestic life as both roommate and occasional provocateur, her competitive streak clashing with a guarded heart. Though perceived as a sister figure by Ryuichi, her dynamic with him thrives on friction—playful jabs and contrived conflicts thinly disguise her yearning for deeper connection, creating a push-pull tension rooted in unvoiced emotions.