Story: 5/10
Never mind the fact that Mirai Nikki lacks any real setup or background information for its battle royale plot (unlike Fate/Zero, which at least sets up the scene and conditions for the Grail Wars), it also has huge glaring plot holes that defy logic and intuition of human behavior. You are often left wondering how the hell some characters (especially Yuuki, the shitty/useless protagonist) could possibly do or not do such a thing, given their predicaments. But this isn't even the worst part, nor is it the cause for why I couldn't enjoy this anime from Episode 2. Besides all that, I thought the concept of different types of Future Diaries was pretty interesting, and definitely had a lot of potential that was absolutely ruined by the main protagonist. But I'll get to that later.
Art: 8/10
Not much to say here. The art is crisp and colorful enough, even though certain scenes could have used more details (especially landscape shots). The characters' expressions are also well-drawn, although at times the characters themselves felt like they were drawn haphazardly.
Sound: 7/10
Decent, but not great by any means. The background music assists in accenting the tone of the scenes, but it does not add to the emotion expressed, nor does it evoke any emotion from the viewer.
Character: 6/10
Actually, I probably would have given this section an 8/10 if it weren't for the utterly despicable and hopeless character that is the main protagonist, Amano Yuukiteru. But I'll get to that. Let's consider a few characters that actually make this anime interesting:
Gasai Yuno: A violent girl with a violent past who is fanatically devoted to Yuuki. I can overlook the obsessive and violent nature of her love for Yuuki, which actually begins to make sense when you see her past with her parents, and how Yuuki is now all that she has left. Although she does make me sick in the stomach sometimes, I understand that this is part of her extremely interesting character.
Uryu Minene: A terrorist who actually works on the side of the protagonist for a while. She also has an interesting, tragic past that contributes to her character development and the attempted character development of Yuuki. Her actions are a direct result of her beliefs, and I have no problem with being able to see how she thinks and acts under the influence of her lonely past, and it gives us all a different perspective.
Kurusu Keigo: A top dog detective who acts for the sake of his family. A necessary and interesting component to the plot, and an interesting character himself. Not much to complain about.
Akise Aru: My absolute favorite choice for replacing Yuuki as the main protagonist. Akise is an aspiring detective with a brilliant mind to match. It is truly a shame that he is nothing more than a supporting character for a very brief amount of time, especially relative to the disgusting amount of time wasted on Yuuki.
I haven't even gotten to Ikusaba Marco and Mikami Ai yet, and already this list of non-Yuuki characters is looking like an excellent mix of personalities and backgrounds. And now we get to the biggest piece of shit in the entire anime...
Amano Yuukiteru: Where do I even begin. Ignoring the fact that Yuuki remains a useless, development-less character for the better part of half the anime, I was shocked to see Yuuki actually REGRESS from character development in Episode 18. He gained some level of resolve (after being a completely pathetic, logic-defying dumbass) but lost it in a grand total of 10 seconds. All in one episode. Wow. If you're familiar with the Hero's Journey character development cycle, you will understand when I say that Yuuki essentially spends 10 episodes in the Abyss and comes out of the wrong side and regresses back into his worthless, hateful self. Primarily because he was so worthless and detestable in this anime, receiving no character development and a TON of screen time, Amano Yuukiteru single-handedly destroyed my enjoyment of the anime, as well as the individual score of the Character section.
Enjoyment: 3/10
Once again, I probably would have rated it much higher (8+) if it wasn't for Amano Yuukiteru. He represents all that a main character should not be. I couldn't care less if he was a side character with less screen time, but the fact that he was the main protagonist and received a disproportionate amount of screen time that could have been for other interesting characters is just an abomination.
Overal: 4/10
Please don't watch Mirai Nikki if you hate hating protagonists.
