In contrast to that personality, her actual face is emotionless. This is said to be the reason why she cannot maintain her self identity.
After receiving this diagnosis, she set out on a journey to learn facial expressions of humans and youkai.
Yes! Speaking of learning, it can only means that one thing!
Ability: Ability to manipulate emotion
A youkai created, after a long time had passed, from the masks used
by the father of Sarugaku performance, Hata no Kawakatsu.
Each mask depicts an emotion, and putting on a mask will change one's emotions.
Those emotions influences those around the wearer, as well.
She has a total of sixty-six masks.
Each and every mask has an emotion assigned to it, but since there are quite too many,
she normally only uses the masks for the four emotions of joy, anger, pathos, and humor.
Because her story is discussed in detail in-game this time, not all of it will be discussed here,
but the incident began with her "Mask of Hope" being lost.
The reason why it was lost is unknown (probably just an accident), but its influence
is what caused the sudden rioting.
Originally, she stabilized herself by having each emotion hold their balance with each other,
but losing just one mask caused her emotions' original powers to interfere with each other, and she went berserk.
In fact, when she's stabilized, she hardly lets any emotions show. She shows interest in nothing,
and aside from when her masks are required, she just quietly acts as a tsukumogami.
Because of that, some say that when she goes berserk, she seems more human-like.