Rin's is tall and has a mature-appearance that corresponds with her personality. She has shortly cut brown hair and hazel eyes with pale skin.
Sensible and calm, Rin is frequently seen giving love advice to Asagi. Because of her intelligence, Kojou occasionally feels as if she is aware that Kojou is not a human, but he still treats him like a normal person.
- The name Rin means "morality" (倫).
- Rin's surname Tsukishima means "construction" (築) (tsuki) and "island" (島) (shima).
- Rin's family is mentioned to be quite well-off, as stated in Volume 6.
- In the manga, Rin had pigtails and wore glasses.
- Rin is a member of the Student Council at Saikai Academy.