The smallest and youngest of the group who tends to interact with Yoh's group more than the others. A sweet little girl with a crush on Lyserg Diethel, in Millie's past she was rejected by her mother.

Somewhat impulsive and a little cocky, Millie is frequently seen in the company of Ellie. Together, the two of them are the first of the Lily Five to appear before Yoh.

She uses a slingshot as her medium. Her Guardian Ghost is Onibi Onibi, who appears in a shape of a fireball with a face of a fox, that when merges with the slingshot becomes a crossbow.