She's a Japanese woman who works as a maid in the house of Kallen's father to be close to her daughter.
She's addicted to a drug called Refrain, which makes it feel like you are in the past, when Japan had not yet been taken over by Britannia. When Kallen sees it thus, and notes that she became a maid to, somehow, take care of her, she now regards her mother one more reason to fight.
In the end, when the world finally becomes a place of peace, it ceases to be employed and one is living with Kallen in a small house.
