The concept of the Yin-Yang is very odd, but it makes sense when you think about it. Duality. Two opposite forces that are interconnected. They work against each other and with each other at once, and anything else throws off the balance of the Earth.
The Yang represents light, energy, and nature. Avatars of Yang therefore are likely to be upbeat or energetic. They will do all the work manually, with as little help from outside as possible. They use power blasts, strength, and force in battle.
The Yin, on the other hand, embodies shadow, calm, and technology. Avatars of Yin are calm, collected, and clever. If given the option, they will choose to use technology, preferably created by them, to do their work. They rely on wit, lightning, and tech in battle.
And that's where they come in; Miko Nakadai and Vincent Kennedy, two people who live in Jasper. He's a Yin, she's a Yang. And of course, they find themselves in conflict with each other. It's gotten to the point where Vincent has started causing trouble under the name Shatter. Nothing major, just enough to anger Miko. Who has taken up the mantle of Commander Fistfight to keep him in check. They fight so often that they know each other's strategies by heart. Their war gives Jasper something to watch, look forward to. Gawk at.
To add to her stress, Miko recently fell in with the Autobots, a war faction of robots from another planet. She's befriended a couple, but their friendship doesn't stop her from keeping her identity secret. Which makes her desire to come along on missions seem all too impulsive. Sucks to be her.