It's the last Aria series. The three apprentices are ready to advance -- Akari and Aika to become primas themselves, and Alice to lose her second glove. This fills them with a mix of excitement and anxiety. Their seniors also see this change coming, and it fills them with a mix of pride and nostalgia.
We get more backstory from the seniors, about the time they were singles, about to become primas. This provides a lot more context, which places the feelings of the younger undines in a context.
There's not much else to say about it. The series has the same visual style as the previous one, the same voice actors.
I was happy to see the series reach a real conclusion, but a bit sad that there won't be any more Aria anime. If you like Aria, you'll have seen this already. If you didn't like Aria, steer clear. For myself, I'll give the series a 8,5.