Story:
The concept is actually really good in my opinion. A mysterious past about getting rejected, and coming back to take "revenge"? And then it is hinted that it was all a misunderstanding?
The romance is MUCH different from shows like Nisekoi. The romance is meant to be forced, and that isn't what you really watch it for. This guy doesn't love Adagaki Aki, so the romance is meant to feel off.
The mystery element is a huge part of why I liked this anime. It is not clear what happened in the past, and new characters are introduced from the past. The small, vague flashbacks are the best parts of the anime in my opinion.
Art: 4/10
The art... was not good. I mean, the art style itself wasn't too bad, but the animation was rather subpar.
Now, is that bad? No. It's a story/character driven anime, not an action anme like Fate/Zero. If you want good animation in a romance, I would recommend Oreshura. However, it is not needed here. The animation is okay, and does not positively or negatively affect my viewing experience.
Music: 6/10
I liked the opening. Many say its rather "cliche", but I found it fine. A lot of anime have this type of 'energetic girl singing" thing, and for good reason. It has been proven to sound good. 7/10 (Also, some say the opening has a lot of spoilers, but as someone who has never read the manga, all of the images are taken out of context, so in reality its not really spoiling anything.)
The ending was... okay? It wasn't particularly good or bad. Okay music, okay animation etc. 5/10.
The OST was also subpar. Not something I would listen to on my own, but didn't destroy the mood or anything. 6/10
Characters:
Every character had some sort of mystery behind them, which was really interesting in my opinion. I found all of the characters very likable, and only one or two characters were particularly irritating.
Enjoyment: 9/10
I actually enjoyed the shit out of this anime. However, some of it is nostalgia and the parellels between this anime and SNAFU were real. I really liked SNAFU, and one of the elements that it included was the "mysterious past" that dragged me in. However, this was a personal taste kind of thing, so although I really enjoyed this anime, I gave it a lower score.
So, without spoilers... the ending was shit. No way around it. It's a manga, so it continues further.
