OK, so, how does all this "Ki" stuff supposedly work?
Obviously, I don't believe in it in real life, but this is a fictional story with fantasy elements, so there's no reason why we can't include it if it fits.
Ki, in real life, is the life force of your body. An easier term for it, would be the bioelectricity that your brain uses to communicate, half assed used to achieve other things. It's the closest thing I've seen to any sort of realistic "Force" in existence.
Acupuncture is used to fix flows of Ki within the body, and though not everyone agrees that it exists, both Acupuncture and Shiatsu were developed by mapping out the flows of Ki within one's body, initially.
But, in real life, there's both the Meridians and Chakras that work for your body. The Chakras are like the big organs that generate and adjust Ki through the body, and when in tune, helps the body keep from getting sick. On the other hand, meridians are like the blood vessels for Ki, so it moves through the body properly.
A picture of the Meridians is here: http://www.healingqigong.org/wp-content/uploads/2010/12/meridians.jpg
And a picture of the chakras, for the traditional showing of only the major ones, is here: http://25.media.tumblr.com/tumblr_m7hzjfaunh1rskgyto1_500.jpg
This is all based off of Chinese martial arts and medicine, mind you. There's all sorts of different names for it. I just call it what I was taught.