Kai is one of the children who was touched by/aspected by a demon, in one of the early appearances of Toro, at Lijuan's wedding. Kai was touched by a demon of dark truths, which she occasionally has shared with the party. In exchange for her help, we worked with Speedy to age her to her maturity.
Some of the dark truths that Kai has told include:
From Lesser of Two Evils: Why humans like spirits better than demons: "She answers that Spirits are about one's nature, and Demons are about one's interactions. Spirits transform humans to be like them, to share their natures, and once they are transformed, there is nothing to object to. Demons want to interact with people without changing them - to set them on fire, to seduce them, to make them awesome - and interactions are often objectionable."
Kai also has (or at least had) a Wisdom mechanic. When we first met her she had zero wisdom, but she can learn a point of Wisdom from a given source. One of the ways she learned a point of Wisdom was when we decided to bring her into her maturity even though we didn't think we'd gain much from it, but because we felt we owed it to her to help her.