Rin Itoshiki is the younger sister of Nozomu Itoshiki. She is the Itoshiki family's fifth child, as well as the only daughter. She is the founder and head teacher in the Itoshiki School of Flower Arranging.
Being a member of the Itoshiki family also entitles her name to have an alternate meaning when its kanji is written sideways. When her name is written horizontally, it becomes zetsurin (絶倫), meaning "unequaled", "unrivaled" or "peerless", but she does not appreciate the name as it is often used as slang for sexual prowess. Rin has a lady-like attitude and is always responsible for holding events in the Itoshiki estate.