I didn't know about this manga or this short before, but after I caught up with the Fall 2017 anime I found out about it and became very interested in it. This is a promotional video made several years before the anime with a very different style.
1. Story- 5/10
Not bad honestly, and it couldn't help the extremely short time lenghth-the a of the story was decent. We were given a brief presentation of the atmosphere-mostly a mysterious drama with plenty of action, and bits of both comedic and tragic moments sprinkled within-but not much else. But yeah, there wasn't much there to learn about, just that a main cast full of gems is fighting against..something...for some reason. You can find out more in the manga or the TV anime.
It's not as good as the currently airing TV show-the CGI really adds to how the characters are gems, and makes the landscape beautiful and vast-but the 2D animation here looks nice, and it makes the characters extremely expressive and full of personality. In a lot of places, especially the backgrounds, it looks a bit flat and lacks depth or complexity however. It just doesn't "pop" as much compared to the TV show.
3. Sound- 6/10
Not much to say. The music is nice at providing atmosphere, but there's extremely limited sound everywhere else-just wind and some other short sounds effects.
The characters are expressive and you get a brief preview of some of their personalities, but not much else.
I definitely enjoyed this promotional video, but that's all it was: a promotional video. It did its job well and that's it.
I advise you watch this before the TV anime as a good hook. It's pretty short, less than two minutes long, so you have nothing to lose. It might hook you in, as the TV show is an absolutely gem (pun intended), and I've heard good things about the manga as well.