It's the Christmas holidays and a weird snowstorm has hit town. Kakeru is an astronomer whose life revolves around things like the impending space shuttle mission, watching the moon and studying some meteor debris he found. Unfortunately the latter is seriously bad news because it's from the meteor on which Princess Snow Kagura is heading for Earth. Kakeru gets sick. (He also neglects his girlfriend Himeko, but that's by the by.)
In summary: you have got to be kidding. This film has lots of great stuff, if by "great stuff" you mean "profound stupidity and breathtaking perversion". It's certainly entertaining. The cut-and-pasted plot is stolen from last year's (superior) film, which suggests that someone hadn't realised that that movie's throwaway storyline was the least interesting thing about it. Admittedly this year's Luna subplot is all-new, but that's probably because no sane person could have imagined it.
As for the perversion... The villain is a topless Ice Queen with buxom Snow Dancer sidekicks. Chibi-Usa gets a nude transformation sequence (gyaaah, my eyes). However best of all, Luna falls in love with a human. Yes, Luna the cat. It's bad enough when she asks Usagi for advice about boyfriends and dating, but I lost it completely when Luna kissed her new amour. Fortunately he's asleep at the time and has no idea that he's the object of a cat's romantic affections. Eventually Luna gets a nude transformation sequence, of all the things I never thought I'd see. Apparently the movie's English version trims that sequence, although personally I'd have thought Chibi-Usa's transformation far more censorable.
Admittedly Luna had a human form in both the manga and the live-action TV series, although the latter's was a little girl instead of a woman. None of that makes this movie any saner. A cat in love with a human. Mmmmm, right. Oh, and don't forget the bit about, "The brave Inner Senshi and the gay Outer Senshi team up to fight a topless woman made of ice".
Incidentally, what about Artemis? (Just as Sailor Moon has a cat called Luna, Sailor Venus has a cat called Artemis.) As far as I could see this film invented an all-new Luna-Artemis relationship out of nowhere. We'd had a few hints in the TV series that Artemis fancied Luna, but it was always one-sided and she always slapped him down. Never had it been as serious as it's painted here. Admittedly Season Four (Sailor Moon Super S) would take this somewhere with Diana, but if you've simply been watching the anime from the beginning this feels like a surreal diversion in a silly movie.
I'm not wild about the script. Artemis conveniently "remembers" a big whack of backstory when the scriptwriters decide it's time for an info-dump. Last year's directorial flair is also absent. Promise of the Rose had kick-arse action scenes courtesy of Kunihiko Ikuhara, but this is little more than an extended TV episode. Oh, and the Outer Senshi are cardboard and wasted. I liked the way they drew the Ice Queen in white lines instead of black, though.
Overall this film is hilarious, sometimes even deliberately. It has a sense of humour and some funny jokes. It was the first Sailor Moon I've seen that's flat-out bad, but it's certainly never boring and it even has heart in its own brain-damaged way. It could be awesome to see this MST3K-ed...