What is it about? I'll be honest, my translation skills did not furnish perfect information on the story, but as I understand it, it's set in a world with two continents at war with one another. During a secret mission, Juana meets the ace pilot Charles and...something happens. Just kidding. They get tangled up in the war, and with each other, romantically of course.
Sorry I couldn't be a bit more descriptive-- but it sounds like a neat story and I gather it's a rather well-respected title. Amazon.co.jp seemed very impressed in their review.
Oh, and I did mention it's Madhouse, right? They seem to really dig these pseudo-WWII-era type stories-- it makes me think of Allison to Lillia, which was also animated by Madhouse.