I marathon-ed this anime in two days.
The story was not the most colorful or elaborate, but it was rich in culture and backstory. I must say, if you are a sucker for backstory, it shall be sated here, rather than left out to wither away in the recesses of space and time, like so many other anime.
The art, while well above average, fell short of remarkable. It made the anime much more visually appealing than I was expecting, and despite the "bishounen" vibe throughout, the characters were not overly flowery and obnoxious in that regard. The environment was done beautifully, with especial care given to the sky and to the castle art.
The sound in this anime was quite nice. I would say it was not necessarily unique or remarkable in the everyday moments, but the anime focuses a lot around the heroine's singing, which is done in such a way the viewer enjoys it more each time, rather than a taxing noise to fast forward through as the producers provide tiring filler content.
The main characters were enticing and colourful, providing a refreshing reprieve from the blase stereotypes of females who are over sensitive and never forgive, and males who are either too brutal or too soft. The heroine is strong, but nothing superhuman, and the male character is emotionally realistic to the experiences he owns. I would say my only desire would have been for the secondary characters to be a bit less flat.
This anime carries a dark and flavorful theme throughout, and I would recommend it to everyone.
