Ruri Kujo (久城瑠璃, Kujō Ruri) is the elder sister of Kazuya Kujo and the only girl among the four Kujo siblings.
She acts as Kazuya's link between his home in Japan and Sauville, where she often sends letters to.
Like Kazuya, she grew in fear of her father and elder brothers, but mostly because of their slovenly behavior. On the contrary, she is kind and protective to Kazuya, and believes he was better born as a girl so that they can play together.
Kazuya's departure to Sauville has left Ruri heartbroken at first, as she was no longer able to share moments with him, but Kazuya's immediate replies to her letters managed to relieve her.
She is currently a student in Seian Girl's School.
She was first mentioned in where she sent Kazuya a shopping list. Among the items in that shopping list was a glass replica of the Blue Rose, the missing prized gem of Sauville. Shopping for the items she asked for was what led Kazuya to find the genuine Blue Rose being auctioned in a department store in Saubreme.
Her first official appearance in the anime was in Gosick episode 12. She appears in Kazuya's flashback as he reminisces memories of summer in Japan.