This review contains soft spoilers (and spelling/grammar mistakes :P maybe).
Lately I find the films that animation studios create disappointing, they waste resources in creating empty, meaningless and forgettable works, that they're visually beautiful doesn't change anything because they don't contribute anything to the industry or to the consumers. This work is just one more and as such I will forget about it and of course I won't recommend it, not that I expect all the anime films I consume to have the narrative quality of Studio Ghibli, far from it, but if there's a team behind it I expect them to be at least competent when it comes to putting together a story with sense and coherence.
The main idea seems good to me, but the development of it isn't, without touching the fantasy elements (which btw have been used terribly bad) it would have been much more correct if it had been a story mainly about survival and that this point wouldn't have been a fleeting resort. It would also have been correct for each character to overcome their traumas/problems thanks to "the power of friendship", that would have given these characters a development and an evolution but no, here we have 2 hours of flat children's characters who simply exist, cry and complain (I had to pause the film several times because I got saturated).
I'm not going to try to fix this nonsense anyway.
I have nothing to say about the animation, is good and consistent, although it doesn't stand out, it's in line with what is currently available in similar productions.
I honestly don't remember the soundtrack and I've only just seen the film.
The voices were of excellent quality (Kana Hanazawa, Mutsumi Tamura, Asami Setō, Ayumu Murase, Inori Minase, Nana Mizuki, Yumiko Kobayashi, Bin Shimada and Daiki Yamashita), I feel sorry for the cast for having to do this job, I hope they have been well paid.
The characters are flat, boring, undeveloped with unbearable and overwhelming conversations. I think choosing teenagers instead of children would have made the drama better. If we put ourselves in reasonable and logical mode, children in that situation would have cried all the time, but dedicating a 2-hour film to them seems ill-advised to me precisely for that reason xd leisure is there to entertain, not to bore or saturate viewers. Btw, Reina's character is horrible, I can understand the stress, overwhelm and anxiety after the events but before that she's unbearable and deserves a slap (or several) to stop being so inconsiderate, selfish and hurtful to others.
In short, I personally don't recommend watching this, it's too many hours wasted and there are other films that are more worthwhile (I have recommendations in my profile if you're interested).