That was almost unwatchable. It's lovely and light, but I was struggling to keep my attention focused. I'd like to rewatch it, partly because it's Masaaki Yuasa being as artistic as usual and partly to see what I missed while I was bouncing off the film so hard. As for Tomoko, she stopped watching after twenty minutes. (Note: other people disagree with me massively here. This is an unusually love-it-or-hate-it film, both in Japan and in the West. It's easy to find reviews with titles like "Night Is Short, Walk On Girl Is The Best Anime Movie In Memory".)
It's the story of a night out, for a generous definition of "story". There's a Black-Haired Girl who wants to enter the adult world, although she also thinks that means alcohol, goofy dancing, meeting loons and participating in a stage musical. She's one of the film's two main characters. The other is her Senpai, who's in love with her and spends all the film trying to meet her.
They have misadventures. It's beautifully, boldly animated. It's very likeable... but personally I couldn't get past the fact that the narrative isn't character-driven. Our two protagonists aren't actually protagonists. They're leaves, drifting down a freeform mega-animated semi-improvisation that thinks it's adapting a novel and is so, so wrong. Crazy scenes happen to them. Occasionally they'll do something significant, but it's rare. This film made my eyes drift shut, no matter how much I fought it.
There's nothing to get a grip on. Little of it means anything, although there are moments. (I liked Mr Depressive Drinking Challenge and how Black-Haired Girl inspiringly triumphs over him twice. "Life is fruitless, lonely and hollow. It's over in an instant.")
The film's based on a Tomihiko Morimi novel, incidentally, making it a reunion for the staff of The Tatami Galaxy in 2010. That was weird too, but I liked it. (This isn't a sequel, by the way, despite a few crossover characters. Yuasa has said that he thinks of the two as being set in parallel universes.) Incidentally, other anime based on Tomihiko Morimi works include The Eccentric Family (which kept getting better and better the more I watched it) and Penguin Highway (which I'm looking forward to greatly).
Noteworthy things include:
A man who's sworn never to change his underwear until he wins the heart of his sworn love. Wouldn't one be a problem with the other?
The god of used books, who explains how all used books are connected.
The musical theatre sequence, with multiple songs.
A wacky dream trial, a bit like the one in the last episode of The Prisoner but with everyone talking much faster.
I was clock-watching. It's all so abstract and free that none of it means anything. For example, there's a particularly wild sequence near the end where Black-Haired Girl is falling towards a bowl of yellow soup, but is saved by an upside-down Senpai grabbing her hands and flying up into the sky with her. This eventually proves to have been a dream sequence, but at the time I couldn't tell. There's no real difference between that and the rest of the film, beyond mere degree. It's just another example of Masaaki Yuasa being playful at the expense of character-driven storytelling. Oh, and it's set in Kyoto but no one speaks in a Kansai accent.
Lots of people loved this film. You might too. I didn't, but I'm not writing it off either and I might well rewatch it one day.