This is How You Lose the Time War

Red and Blue fascinate each other

On opposite ends of a time war Red and Blue are agents often pitted against each other -- one from a side grounded in technology and the other in the natural world. Each affecting history through detailed machinations. And then one day Blue leaves Red a letter both praising and taunting her. She responds in kind. And so, begins a strange and wonderful friendship that develops into much more.