1. Kumiho happening was completely accidental. I love telling this story, so most people already know it, but I'll repeat it again. When Kuna was researching Asian foxes, she happened to mention the kumiho to me as being a crazy evil fuck-your-shit-up-and-all-your-family's-shit-up fox. I didn't think of it much at the time, but a day or so after this voice popped up in my head. I kept associating it with the kumiho, but tried to place it to other characters [unsuccessfully]. Eventually I put them together and sparks flew. Once I actually started researching her, I fell in love with the mythology, and the rest was history.
2. I'm not sure Kumiho has good traits. However, though she mostly uses it for evil, Kumiho is amazingly clever. Part of it comes with being a fox, and part of it is just how her mind works.
3. While mostly her rage is for show, sometimes Kumiho tends to let her genuine anger get the best of her. She still acts within her tricksy, calculated bounds, but sometimes will blatantly ignore logic and her better knowledge in order to get revenge, or anything she really really wants.
4. Writing Kumi is cake. She is delightful and wonderful. Figuring out the workings of her mind is... delightful, but also confusing and scary sometimes.
5. Doesn't exist yet. Not until the future, perhaps, when much of Kumi's inner workings will be revealed. Still, she's so complicated that it's hard to define her in just one log or post, much less a phrase or simply a line.
6. Continue along her line with Ray's relationship, and with that delve further into revealing her personality to the general public. Establish more communications and hijinks, as always.