Ungaikyou - Kyou

The mirror which exists by Gold Rock, Bullet Butler's world. An artifact spirit raised and created by Ungaikyou - Sui by using a small fragment of her own soul.
Contrasting Sui, she's more humble, she tends to devote herself toward her elder sister. One thing they both share to the same degree is their incredibly strong sense of duty.
She doesn't understand the behavior and psychology of humans, so she tries to ascertain them by watching their way of life.