高城 七七

The younger sister of Natsume and Shuugo. Currently enrolled in Kayou 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 Shuugo's attempts to dissuade her.