Raido's unnamed younger sister attends junior high school during her brother Shota Raido's high school years. She bears a strong resemblance to Raido, sharing similar hairstyle and facial features, but radiates a wider spectrum of visible emotions compared to his typically expressionless face. Her standard outfit is a white sailor uniform with a navy blue skirt, white short socks, and black penny loafers.

Her personality blends outwardly blunt communication with underlying concern for her brother. She frequently calls Raido a "sort of an odd guy," voicing skepticism about his social skills, especially his ability to make friends. This surface criticism masks genuine familial care, as she privately worries about his well-being and social life. Her expressive reactions visually contrast Raido's stoicism, making her thoughts and feelings immediately clear through her face.

Their sibling relationship unfolds through everyday moments. She occasionally assists Raido, like practicing lip-reading. During one session, she pretended he had succeeded when he hadn't, leading to temporary confusion until he self-corrected. Later, demonstrating remorse for perceived coldness, she gave him a hand spinner as a peace offering. These small acts reveal her unspoken affection beneath habitual teasing.

Her independent life includes friendship with Eru Aharen, Reina's younger sister, as classmates at the same junior high, maintained separately from Raido's connection to Reina. Observational moments show her relaxing at home, often reading books while lying on the couch. When Raido seeks her advice, her responses lean toward pragmatic realism over emotional reassurance.

A childhood flashback reveals an incident where Raido ate her pudding without permission, causing significant distress and tears, adding to their complex but caring dynamic. Her character remains consistent, maintaining her distinctive mix of sarcastic commentary and quiet support without major changes beyond established patterns.