Tsukumo Kuon

Kuon is an rather talented artist who specializes in painting depictions of sadness and despair. She is rumored to be 'cursed', as a series of tragedies have followed her in the past. In order to paint her best, she needs to be able to express her own immense sadness - thus, she burns bridges with her only friend and creates the best piece she's ever made.

From Giko's Girl Dictionary:

A girl who holds dear sorrow.

Through my observations, I have recently discovered that a personal world exists within each and every girl. Among them, Kuon's rejection of other people entering hers appears to be abnormally strong. Very interesting.

It also seems that she'll be staying at the dorm from now on, which makes for a wonderful opportunity to observe her closely.