We all have our hour upon the stage, or our 25 minutes to be exact, and that's more or less what Kakedasu Monaka is, an episode through the eyes of 'Team Monaka', the people (mostly just Katou) who failed to qualify in the Wind Ensemble, and the depiction of their role within the competition, a bit unfortunate for them that even when they're technically the main characters, they still have a supportive role, but no matter, it's an episode about Katou, and her accomplices in Team Monaka, and how the big day unfolded, from their perspective. When all's said and done, this is basically a regularepisode of Hibike but this time around Katou's the main character, and, there's all the goodness that you'd see in a typical episode, made marginally different on account of the fact that Team Monaka consists of different people than the performers in the Wind Ensemble, and also the fact Katou has different things that she needs to do compared to Kumiko, but, in recognition of the fact that this was a one-time ordeal, they certainly pulled no punches, which was a good move on their part, since if we're going to get one episode from the perspective of a different character, they might as well make it eventful, and that they do, while high octane isn't something that's usually a particularly fitting description of a high school drama, this time, it is, there's plenty of desperation seen, and, of course, there's a shot of Katou jumping into the sky at one point, because if they've got one episode on their hands, they might as well go for it.
All in all, Kakedasu Monaka's a perfectly valid addition to the Hibike Euphonium series, usually with OVAs you can expect them to put in less effort, but not this time around, in fact, the opposite, when one considers the closing 5 minutes or so, the impression I get is that in the knowledge that this was the only episode they had with Katou as a main character, they chose to make the most of it, and it's certainly a fuller experience than most single episodes of the original series. While under most circumstances I'd say if you decide to skip an OVA you're not going to miss out on much, not this time around, this episode is undoubtedly a fine addition to the series, with as much character and heart put into it as any regular episode, if not more so.