A sequel to the main series and follows the Aqours girls as they prepare to enroll at a new school. While the first and second years run into some unexpected trouble, the third years end up going mysteriously missing on the way to their graduation trip. Separated, the girls begin to realize the value of their friendships as they attempt to find a solution to their various crises.
Love Live is part of a bigger multimedia franchise. This is important to consider because the Anime serves more or less as an advertisment for the games and to create a basic level of attachment to its characters. I don't think it's justified to call the Anime adaptations a cashgrab, but all of them so far have been pretty mediocre and anyone who has seen Love Live Sunshine (LLS) knows what the expect from the movie.
If you happened to like LLS, that's great. You will probably like "Over the Rainbow" (OTR) too, as it does essentially nothing different from the TV series.
If you didn't like the TV series, well that's too bad. You probably won't like OTR either. The movie managed to leave behind the forced drama about Aquors' beloved school closing but at the same time it introduced new unnecessary drama.
Like the TV series, the movie lives off mostly of the cute interactions between the members of Aquors. Everyone has retained their quirks and they are used for comedy throughout the movie. We get to see a lot of new musical performances which makes you feel like you're watching disney movie because the characters happen to sing and dance in the most unlikely of situations. Sometime during the movie it became clear to me that the story of the movie is just an excuse to show the characters' new performances. This is also where the movie differs a bit from the TV series: There is no longer any driving force behind Aquors trying to perform as school idols. Heck, there is no longer any driving force behind the story at all. The TV series concluded it perfectly with Uranohoshi closing and merging with another school. And here we are in OTR, with Aquors thinking about how to continue their lives, now that Dia, Kanan and Mari have graduated.
The trip to Italy could have been a great adventure if it hadn't been botchered by the reason of why Dia, Kanan and Mari disappeared. As it turns out, Mari's mother tries to force her into an arranged marriage to restrict her freedom. An interesting turn of events, but the way it's resolved is in typical LLS fashion: Mari convinces her mother to cancel the marriage if Mari can show her that she can make people happy while performing as a school idol. Of course, her mother agrees and Mari manages to persuade her later on. I know that drama has never been a strength of Love Live, but come on ... that whole arc was really laughable.
Dragging through the movie is generic ganbatte talk. The characters are motivating each other a lot, but that's really only on a superficial level. It has been like that in the TV series as well and it's continuing in the movie. Combine this with the fact that there is no competition anymore and you may start wondering what kind of goal our characters have in mind. At the beginning of the movie, it is clear that due to Dia, Kanan and Mari having graduated, the remaining members of Aquors have trouble performing at their full potential due to lacking 3 members. Fast forward to the end of the movie, they suddenly are able to perform with only 6 members, despite having learned exactly nothing.
Aside from Mari's arranged marriage, other subplots have been introduced during the movie as well. One example would be Leah from Saint Snow having trouble to assemble a new school idol unit, now that she can't perform with Sarah anymore. This subplot, like all others, was left severely underdeveloped and it's resolve was basically pulled out of thin air. A new character was introduced as well, You's cousin Tsuki, but she didn't really serve any purpose besides just exisiting.
Music should be one of the greater strengths of Love Live, yet I find most of the songs to be pretty generic J-pop. I have no deeper attachment to any of Aquors' members (neither to the Anime characters nor the real singers) and with the exception of "Mirai Ticket" I have not found myself to really enjoy any other of their songs. Maybe I'm not the target audience of Love Live, but I don't see what makes the music any different from other idol groups.
My rating of 4 may seem harsh, but you should put it into your own perspective. It's the same rating I gave the TV series because I think the movie is just "as good" or "as bad", depending on your perspective. As I said in the beginning, if you liked LLS you will probably like the movie too. But looking at LLS as a standalone Anime, I think it's just bad. It's bland characters, bad story, forced melodrama, repetitive comedy and average music all makes it a bad Anime for me. Sadly, the movie offers no real development and makes the same mistakes. That's why I think only fans of LLS will love it. It's certainly not made for a general audience.