Katia's love, whom she fears will do something stupid if the Huanxin Jinx arrangement falls through.
In the quiet after Katia's Worst Memory, Katia tells Carl she is worried about Daniel, specifically that he will do something stupid if the thing with Huanxin Jinx does not work out. Carl says he is worried about him too, and that Daniel loves her.
Katia agrees that she loves him back, but then makes a deliberate distinction: as much as she loves Daniel, she wants Carl to know that she loves Carl and Donut more, as much as she ever loved the woman and infant dancing in front of them in the memory.
Not described in this chapter.
Katia's partner, and the person she and Carl both fear will act recklessly.
Also appears in books you've already read — spoiler-safe to their endings: