WTF was that ending?!!?! That escalated really really quickly, we had absolutely no hint that this would happen. (view spoiler)[ When did Ruuel start showing any kind of emotion towards Cass? I know he is cold, detached and "militarish" but if one has affection for someone there is no way of not showing it, at least with a smile in a moment of weakness! The only two tiny moments where when Ruuel woke up Cass from a nightmare (he had an amused smile and caressed her cheek) and when he was sleeping guarding Cass and she hurt herself while having a nightmare (where he hugs her while being grey). I don't get it. The author should have written him to show a little more emotion or confusion to make the last part believable. (hide spoiler)] -1 star for this. 
 Although I'm annoyed about the ending, I can't take more stars because the plot is still very interesting, original and unpredictable. We uncover some secrets from Muina, but they generate more questions making the series sill very enjoyable. You are as lost to what's happening as the characters in the book. Cass discovers that she has more in her than just an enhancement ability, and this new unknown abilities create a lot of problems as nobody knows how they work and their limits. Cass is still a teenager so as her fixation on Ruuel increases, so does her writing about her feelings of him on her diary. It isn't annoying or cheesy though. 
 One thing I really like about this series is that, although Tare's culture and government are really different from ours in some aspects, and KOTIS command is really strict, the author doesn't portray them as the villains or enemy. They are just a different government following their rules and doing their best to manage the ongoing war and the investigation of what really happen on Muina all those years ago. It may seem that they use Cass as a weapon but they take care of her, are interested in her opinions and just do what they think it's best for her. It may be convenient for them, but they are not the villains in this series. 
 Beginning the 3rd and last book now, I really hope it has a great ending.