My main gripe is that this wasn't long enough to actually develop half the characters. Despite that, I really did enjoy the feels trip this takes you on.
The animation is pretty standard, but very pretty. The music serves to make you feel pretty sad at the right times, and the sound creates a very immersive atmosphere.
The story itself feels incomplete as the story really has no time to build to any sort of resolution, although it does try.
I feel like all the pieces are here to have a very good 1 season long anime, or maybe just a full feature length movie, but
as an OVA, it's mediocre. That said, it's definitely worth your time to see.