高城 七七

Shugo’s younger sister. Currently enrolled in Kayo Private Academy, located in Ueno. 

A genius girl, with encyclopedic knowledge and a strong memory. Her eccentric words and deeds worry her brother, though she pays that no mind. 

Incredibly interested in the bizarre serial murders in Ueno, she begins her own investigation despite Shugo’s attempts to dissuade her.

MangaGamer

Also the little sister of Natsume from Kara no Shoujo.