The chimaera are like something out of an artist's imagination; they're these weird human-animal hybrid thingies. Most people think that they are just figments of Karou's imagination. They think they only live in her sketchbook. But they're real.
Chimaera are people, too. Well, not really. But they just want to yearn, ache, love, and shop like the rest of us.
Even though they are an entire race of people things, we don't get to know too many of them. We've got separate pages for "Brimstone," "Madrigal," and "Thiago," but there are two more worth mentioning: Issa, the snake goddess with serpent coils, and Chiro, Madrigal's sister.
Issa is who Karou calls the "guardian of the threshold" (5.10). Her job is to protect Brimstone's shop from the outside world. But she also yearns to see the outside world, as we realize when she looks at Karou's sketchbooks and comments on things we would otherwise find mundane. She's also kind and nurturing toward Karou, so girls' the closest thing our favorite orphan has to a mother.
Chiro is a little different. She's petty, insecure, and vindictive. Hey, she's just like us humans, when you think about it. She's jealous of her sister's good looks, and sells her out when she finds out about her affair. Her tattling leads to her sister's death, but she doesn't even seem that upset about it.
Of course, Chiro and Issa live in a world of death. These are people who are constantly at war. In war, people become statistics, and it's hard to see them as real people, with their own personalities, hopes, wishes, and dreams. Issa and Chiro show us the human side of the beast war, for good and for bad.