An interesting look into the lives of Helene and Elias when they were young, and seeing their friend Tavi. I don't remember if he was mentioned much or at all in the main series. But it's kind of sad to see that even when they were barely teenagers Helene was even more brainwashed into being a soldier for the empire. That she was fully committed and willing to die for "the cause" during a training exercise, willing to kill her classmates for it.
Elias, even back then wasn't willing to break his personal code for the empire. I know there is a second one, but I really hope there will be more.