The only problem was the main character - Nina. During the light-hearted beginning of the anime she is a likeable, happy-go-lucky protagonist akin to the typical hotheaded shounen protagonist. However as the anime quickly develops towards more dark and political themes she becomes incredibly out of place. She remains nothing more than a child throughout the show, seemingly unable to take anything seriously even when the lives of other character's are at risk. During several tense and important plot points she simply responds to everything with "I don't understand" while the rest of the characters move the plot forward around her. Several times when she is given pivotal tasks to complete for the good of the cause she fails to do them simply because she wandered off to do something else without a second thought for the consequences.
And it's a shame as most of the other characters are very strong. They are well designed both personality-wise and design-wise, relatable and interesting. While you could try to ignore Nina and focus on the rest of the cast, she is the main character and as such is involved most things. An intense scene will happen and then we'll be back with her, acting moronic and over-reacting to everything she sees in a babyish voice. By comparison, the plot and other characters become harder to take seriously as they are reacting to her as though she is an intelligent, mature adult, and as though she understands the significance of what they are telling her.
This is particularly potent when it comes to the main romance of the show. Nina develops a romance with a serious, powerful man with the world on his shoulders and an intense drive which pushes the plot forward at every turn. There are some very romantic scenes, but it is simply impossible to buy into - that such a man would have any interest in a juvenile moron that has no awareness of what is going on around her.
Occasionally I took issue with the plot, there are plenty of cliches, deus ex machina, and things that feel contrived just to continue the plot. It's not too difficult to see where the plot is going, but it's an enjoyable ride. Despite going off on the negatives of this show, I don't regret watching it and it did make a special impression on me.
