Christopher Bird’s review published on Letterboxd :
It's exceedingly slow and the buildup is so steady and slow that at about the hour mark you can be forgiven for wondering when Things Are Going To Start Happening; it's almost agonizing. But, happily, the film rewards your patience by forcing its characters through horrible wartime disasters, and the buildup then makes sense because this really is a profoundly anti-war film, and remarkably honest in how it goes about portraying that viewpoint.
Like, when the lead character loses her shit after hearing the Emperor's surrender address on the radio, that's real, because the thing about suffering in war fought on this scale is that you have to keep telling yourself that this is somehow worth it, that not just the death and destruction and physical and emotional pain but also all the awful littler shit like rationing and having to bulk out your food supply with edible plants and having to build a damn bombshelter and not being able to sketch the fucking sea because the stupid military thinks "what if you're a spy" is worth it, because if it's not worth it then what the fuck have you been doing all this time? The entire movie is like this. Entire conversations are had where you know both characters are in denial, and you know THEY know to some extent, and that's just how it is. This is a movie which understands that in war awful things happen all the time, so when the atomic bombs finally drop it's still dramatic but it's also just one more thing on the pile, because everybody has become used to everything being terrible.
Beautifully animated (it reminds me of nothing so much as Raymond Briggs' animation in a Japanese context) and lovely vocal performances, both the original and English dub tracks. It will try your patience, but it's worth sticking it out.