This is just another short episode for the show, and a good one at that - right up until the end. There's nothing wrong with the plot, I think the episode as a whole was the best from the whole show - except for one scene. Non-plot Spoiler: They decided we need a shower scene at the end, there was nothing of the sort in the original 12 episodes, and no fanservice right up until this point. I don't mind fanservice, but this felt very weird considering what the show was about. Sure, showers take place every day, but there was no reason for the final scene inthis cute short series to include one.
If you think fanservice of your cute girls would somehow ruin the experience for you, just stop watching as it begins - since no final message or moral was conveyed that was not portrayed earlier in this episode.

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Generally I felt this episode could have been a 7, except for the fanservice shoved in your face bit.