If you want to enjoy this fully, please watch The Tatami Galaxy first, otherwise, you'll miss some fun little details, and a portion of the symbolism won't make any sense.
Though technically a movie, I'd separate its contents into 3 episodes following our two characters (the female lead under the moniker Kohai, and the male lead as Senpai); the first 2 episodes following Kohai's tenacious approach to life in a night that refuses to end, and the last being a powerful symbolic take on getting through to someone you love.
Following The Tatami Galaxy, The Night is Short, Walk On Girl's star Kohai, is the embodiment of its message, to take life by the horns. With her ceaseless optimism, Kohai doesn't let a single opportunity to live life pass her by without giving it a chance, her character alone is deeply inspirational. With visuals even more brilliantly thought out backed by the most emotionally placed soundtrack, we're transported to that long vibrant night, in Pontocho.
If the first 2 episodes and final act were presented as separate pieces they both would've been improved massively, instead, they connect the two using a glue stick they found on the side of the road, and the movie suffers for it.
*complaint about the final act contains spoilers*
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The problem with the final episode: The only union between this and the other two episodes, and where I wish the movie would've taken it, is the lesson Kohai learns from The Director; always pressing forward without taking the time to look back is also going to leave you blind to other opportunities. Luckily (and I cannot stress luckily enough) for Senpai she just happens to randomly decide from this lesson that she's in love with him. There is no reason for Kohai to love the cowardly stalker, that is Senpai, the embodiment of the flaws that The Tatami Galaxy shines on, a man she hasn't shared more than brief greetings with, even so, this is the path the movie takes.
In its own right, this conclusion would be fantastic given its ocean of gorgeously animated, carefully crafted symbolism showing how, despite his own lack of awareness, Senpai desperately pushes away the love which he so hopelessly desires. Only to be saved from his own self-imposed prison by Kohai. If their past was more obscure, as it would be if this piece was alone then it would have worked. Within the context of the movie though, they should've made it either about friendship or fleshed out a deeper connection between them that was previously unnoticed by Kohai.
Despite my ranting, I do it out of love for the movie and the sting of its so transparently lost potential. Just under a 9/10.