Yeah~ I gave this a 10 ^^ I haven't played the game so I don't know if this OVA does it justice or not, but I enjoyed it anyway.
Story
I've never seen anything quite like it. I will not go into what the story is about because it's in the summary up at the top, but it's very different from all those other 2-3 episode long OVAs out there. It is beautiful and different and is very well presented, even though there was only 2 episodes to work with. If it were to become a proper TV series then I'm sure it would be popular :3
Animation
Not particularly outstanding. Like most other short OVAs it had rather beautiful art, but it wasn't that amazing. Some of the characters could have done with a bit more detail here and there to make them pretty much perfect.
Sound
The opening song is by Nana Mizuki, and I know this is slightly biased but that automatically made me give the sound a 8/10. My score was then pushed up to a 9/10 because the OP and ED are beautiful, and I know I say this in every review, but they fit so well with the series. They really did.
Character
Not enough character development for some of the characters. However, the main couple and Ai were filled out nicely and weren't boring standard 2D characters. They had a personality and were different from the other usual OVA characters. Nicely done development for those two, but not really for anyone else unfortunately. If there had been more episodes then I'm sure all the characters' personalities would have filled out more.
Enjoyment
I always skim-watch through short OVAs like these because I just know they're going to be a repeat of all the others and will be boring. This one, however, is a stand-alone decent OVA. It kept me interested the entire time and I didn't keep looking at how long it had left, thinking "just hurry up and end". I was really sad when it finished and I wanted more! Absolutely loved it ♥