As it is short, around a half hour total in length across the four episodes, I'd recommend it if you need or want more out of the characters of Symphogear XV, though it certainly isn't a necessary piece of the series to view for more casual watchers.
Story: There isn't much in the way of an overarching story between the episodes, but many of the segments/skits within the episodes are linked with one another, or connected to the main Symphogear plotline in some way.
Art: Was fitting for the type of content shown in these episodes, one could perhaps even say it was charming, in a way.
