TL;DR; OVA is a fun story that showcases the characters outside of their school curriculum which has no impact on the main series' story.
Well, Art and Sound have similar standard to the main series, so I won't elaborate any more than that the Halloween themed musicals are entertaining.
Story and Character-
Story-wise, this is a fun, interesting story about Halloween that is like a little peek into the characters' life outside of their school environment. Is refreshing to see how they interact with each other and the fun storylines also bring out their connections with each other really well. There main mix here is definitely Comedy and Slice of Life. The lightheartedness of the OVA presented the characters with more familiarity, where they acted more like the kids/young adults that they are. There is of course no character developments here, but the insight of the characters' bonds are amusing to watch.
