I've started to write this about six times. Every time I start, something happens, like we lose power or I end up in hospital or my mother thinks I'm addicted to my PC (never mind that even if I was, it's holidays, but ANYWAY), so hopefully this time I don't lose power.
Kisa's from a family where certain members are possessed by the spirits of the Chinese Zodiac. What this fully means is kept somewhat vague in the manga, but it's stated that when they are hugged by people of the opposite gender, the Sohma transforms into the animal they're possessed by (at the same physical development as they are at), there's an implication that they have an innate ability to draw "their" animal to them and they also share a connection with Akito, the head of their family. This connection is best described as a mixture of love and fear -- they cannot help but love Akito and they cannot help but fear Akito. Some of the cursed Sohmas have actually been given to Akito by their families or abandoned because of what they are -- Kisa, however, is not one of them. Kisa, actually, has a very good relationship with her mother, if slightly over-protective. We don't actually see any mention of her father at all, and I'm almost inclined to say that she doesn't have one, but not quite that inclined. That sentence made better sense in my head.
Kisa herself is a very hesitant, lonely and sweet young lady. She wasn't always so hesitant, however upon starting junior high school, she was teased and then ostracised for her eye and hair colour. While initially she attempted to defend herself, the teasing grew worse. Finally, she started to ignore the teasing, and all that did was ensure that whenever she did speak, people would only acknowledge her presence long enough to laugh at her, and then go back to ignoring her. Demonstrating that Pavlov knew what he was talking about, Kisa first stopped speaking, then attending school and then finally running away from home, because she didn't want to tell her mother how bad the bullying was. Thanks to Tohru, Kisa now speaks, but she is contantly worried that when she says something, someone is going to laugh at her for it. She wants people to like her, she desperately wants friends, but isn't quite sure how to go about it. Afraid of offending people, she apologises when she doesn't really need to, she stutters and stammers, her voice drops in volume and she generally always gives the impression of vulnerability.
The fact that she has friends at this camp, and people like her, is a fact that startles Kisa. She doesn't know what she's doing differently to what she's doing at home, and yet here people seem to like her and want to talk to her without laughing at her. She's not sure how this happened, and doesn't want to think about it too much for fear of it going away again. As such, she's very hesitant about it, not entirely sure how to go about keeping her friendships and is very...stilted for lack of a better word. This might also be because I'm not necessarily a sweet, kind person, so yeah. Anyway, moving right along.
As mentioned above, Kisa both loves and fears Akito, the head of her family. Akito has a bit of a control issue problem, in that the only person who the Sohmas are allowed to love is Akito. That's somewhat easier said than done, and the younger Sohmas are off forming relationships. One such proto-relationship is that between Kisa and her younger cousin, Hiro. Hiro, however, told Akito that he really liked Kisa and Akito was not exactly understanding. In the anime, Akito backhands Kisa into a wall, whereas in the manga, Kisa is beaten so brutally that she remains in bed for two weeks. She probably should have gone to the hospital for that, but the Sohmas have their own private doctor (yet another one of the cursed Sohmas -- Hatori, who is possessed by the seahorse dragon) and this neatly forestalls a possible abuse charge. Akito also is verbally and emotionally abusive to the Sohmas, presumably as this gives Akito a sense of power to maintain the dependent relationship the Sohmas have upon her.
Kisa herself suffers from a few psychological tics (doesn't everyone?) -- she occasionally has nightmares, generally about being alone, failing, Akito bitch-slapping her into next month for something she doesn't understand (Kisa's from the first half of chapter 104, not the second. Yeah, it's messy, but she can't have had the conversation with Hiro if he's been at camp). Surprisingly, one of them isn't being touched, however she's cultivating that so that people don't hug her and she gives away the family secret. After both Count D and Sanzo brought it to her attention that people are already suspicious of her and her family, Kisa is one apprehensive thirteen year old, and although she is attempting to pass as a very ordinary, misplaced thirteen year old girl, with absolutely nothing special about her, she's not doing very well.
...well, that wasn't as long as I thought it would be.