Aono Morimiya

Aono is Yorito's older sister who has been sickly ever since she was born and is hospitalized at the beginning of the story. She has a cold personality, showing very little emotion but still is visibly annoyed at Yorito for how much he seems to ignore her to do other things. Every time Yorito brings her a new doll, she takes one look at it and throws it in a nearby basket filled with other dolls. However, she does not hate them and even has one which is her favorite - the first one Yorito brought her. She enjoys origami and is friends with Koyori.

[Spoiler] Aono is actually not human, but a Yaka - she was transformed into one by Matsuri when she tried to commit suicide after the Yorito from her time was killed. She has the power to control paper. [/Spoiler]

(Source: Wikipedia)