The movie is a bit messy, but the general premise is that child Miyuki in a flashback found a book in a series of books up for adoption and liked the main character Nico. The issue was that Nico's story (of being trapped in the Demon King's castle) was unfinished (the pages were torn out), so Miyuki decided to finish the story but apparently gave up after being unable to. Back to the present, the Cures go to a Picture Book Festival which just so happens to be in town and see a movie about Nico. She comes out of the movie with some demons, which fight the Cures with a huge bag that sucks stuff up (literally), but the girls fight and rescue Nico. She rewards them with a trip to the World of Picture Books, and....honestly, this honestly feels REALLY contrived, seeing as there's already a HUGE crossover between picture books and fairytales, but there's even more mythological and fairytale references in this movie than the series itself. The issue is that most of them might not be well-known enough to the west; for instance, Akane becomes "The One-Inch Tall Man," Nao becomes Urashima Taro, and Reika becomes Momotarou. I'm not sure how wide the crossover between "magical girl fans" and "ancient Japanese fairytale fans" is, but I'm guessing....not that high, considering this series is aimed at little girls, who likely wouldn't even know those stories to begin with, let alone that they're essentially being parodied. Eventually, the stories begin to fall apart, with the real protagonists of the respective stories appearing in the wrong stories; they become angry at and blame the girls, who wind up in a conveniently five-way connected open desert-like ring. Also, Cinderella is GIANT for some reason. Nico appears, revealing she's the antagonist responsible for causing everything. But not really. It's actually Miyuki's fault you see, for not finishing her fairytale. Because the word of a five-year-old should always be taken to heart, yes....Anyway, she uses her angst of being trapped in the castle with the Demon King to justify tormenting the girls, since Miyuki's refusal to finish the story apparently set off a chain reaction that dismantled the logic of other fairy ta-You know what, this is the suspension of disbelief. I don't even know if I can believe in the main conflict anymore; either that, or Nico did all of this as an act of petty revenge to "take away Miyuki's smile" and hate her. Miyuki's friends give her a pick-me-up speech and convince her to apologize and get Nico to forgive her. Honestly, I think both of them should be apologizing over how little this plot was even explained; it wasn't even mentioned why the pages were ripped out, why the books were being put for charity, or why Miyuki seemingly forgot about this entire plot for about 9 years. They have a fight against all the story antagonists in the Demon King's castle (who grows stronger and is possessing Nico), though they're helped by the "Cow King" from a story I can't remember the name of and Miyuki gets to apologize to an unwilling Nico, saying Nico taught her to remember how to smile. It's nice but it doesn't exactly do the plot justice. Eventually, she realizes Miyuki's true feelings just in time for the Demon King to betray her and attack Nico. Miyuki pulls a Tuxedo Mask and saves her at the last second, getting herself injured as Nico mouths "I love you." Since the Royal Rainbow Burst failed, everyone uses their MacGuffins Miracle Lights to power up Miyuki into ULTRA MIYUKI, aka Ultra Cure Happy. She saves the Demon King with her friends, who reverts to a little shadow-like form seen earlier, and he gets to live in harmony, with Nico apologizing and telling Miyuki she loves her again. (Miyuki was unconscious the first time.) Miyuki cries and we get a nice happy ending.
..Except not really. A lot of the things in the movie were left unexplained or weren't really given the amount of detail they deserved, and the Demon King should probably be reworked completely in my opinion. It wasn't the worst movie I've ever seen, but for Precure, I somewhat had my standards high for this movie, and I suppose that was my mistake. Nevertheless, while I did appreciate the references to various fairytales, many of these references would likely be lost on western viewers, unless one was either raised in Japan or actively researched to learn about these fields. Overall, in my opinion, the movie is too niche in order to fulfill the impact it likely wishes to create. 6/10!