Fuyumi Ootori-Shido is Kyoya's older sister. She is shown to be a bright and sweet-natured young woman who is married, though she seems to spend considerable time with her younger brother and is friendly with Tamaki, who shares an interest in commoner cuisine with her. Fuyumi appears in Ep 24 - And so Kyoya Met Him! which is primarily a flashback of Kyoya's meeting Tamaki and their initial interactions while both are in middle school.
In the anime, Fuyumi enters Kyoya's bedroom and begins tidying up what she perceives to be over-stuffed bureau drawers, which Kyoya tells her to leave be. Still she insists, going on to chat with him about the demands made upon Kyoya by their father who, she learns, has insisted that Kyoya befriend the "new kid at school" - the son of Ouran Academy's chairman - Tamaki Suoh. Fuyumi clearly cares for her younger brother and tries to help him in life, reminding him that he doesn't have to push himself so hard because he already does everything remarkably well. Time and time again, she listens as Kyoya rants about the sight-seeing that Tamaki is having him arrange and in a side-bar, Fuyumi's thoughts reveals that although Kyoya is annoyed with him, she's secretly glad to see him react with genuine emotion. When Tamaki actually visits the Ootori home, it is Fuyumi who recognizes him as Kyoya's "friend" and stands beside Kyoya as they listen to Tamaki play the piano. It is revealed in the manga that she is in an arranged marriage to a man of the surname Shido, but it is a love match. When she returns home for a brief visit, she is chided by her father for not being at her own home, taking care of it. Fuyumi and Tamaki are pursuing a tour of commoners' food together and have a pleasant relationship.