The twenty-first Detective Conan (Case Closed) film, Detective Conan: The Crimson Love Letter, brings viewers someplace they're more likely to be familiar with from an entirely different series: a karuta tournament. Having some familiarity with Chihayafuru may actually be a boon for viewers, not just because karuta is a central theme of this film, but also because The Crimson Love Letter doesn't take any time to actually explain karuta. While it's hard to fault them for that too much – the movie was made for Japanese audiences and is primarily a murder mystery – there are definitely some pieces that will get lost if you don't know the basics. I watched this with someone who didn't know anything about the game and ended up spending a fair amount of time explaining bits and pieces of it so that the entirety of the plot made sense to her.

When you come down it, though, really the most important thing to know is that karuta cards are printed with poems from Hyakunin Isshun, an anthology of great tanka by various authors, and that a lot of them are love poems. This almost immediately gives the title of the film a bit more context – tanka were often used in correspondence (particularly in the Heian era), so a love poem could easily be termed a love letter. Crimson, of course, can refer to the color of blood, although it forms two other visual cues in the movie as well: fire and the color of maple leaves in the fall. Maple leaves are a symbol that come up in many Heian tanka, and there are a series of karuta cards that use maple-themed poems, so the moment one of the competitors turns out to be named Momiji (a word for maple), the image of autumn leaves as crimson should come to mind. It's a very interesting color-based thread to trace through the movie, both in terms of the art and the symbolism, and following it can definitely lead you to some clues.

Because Detective Conan is, by and large, what's known as a fair play mystery (meaning it's possible to solve the crimes alongside the detectives), that connection between karuta, color, and the title is an important one. It is not, however, the only major puzzle piece that we get to follow – this franchise tends to be very good with keeping things fair play, and there's a nice mix of obvious and more obscure clues that we can find as Conan and Heiji work with the police – and independently, because there's always that one cop who has an issue trusting the high school kids for some reason – and they're sometimes clues that we have to pick up for ourselves, which makes the process more fun. Conan does have his gadgets, but those are mostly used to escape from burning buildings; Heiji's dirt bike gets a lot more use in the actual crime solving, mostly as occasionally ridiculous transportation. (It's nearly indestructible, which somehow feels more credulity-straining than Conan's radar glasses.) The mystery plot is genuinely interesting and takes a lot of twists along the way to solving it.

The karuta plot serves as both the frame that supports the film as a whole and the glue that holds together the mystery and the romantic subplot. Heiji and Kazuha form the basis of the latter, and while it has its moments (mostly towards the end), it's definitely not as good as the mystery. Mostly this is because Momiji is such an obviously artificial obstacle; even if she wasn't goading Kazuha into making ill-advised bets on the outcome of their match, her attachment to Heiji is so silly and flimsy that it's hard to take seriously in a story where people get their arms broken by shrapnel from an explosion and suffer from smoke inhalation. On the other hand, there's definitely something to watch for in Kazuha and Momiji's showdown that provides one of the major hints as to the root cause of the destruction taking place, so perhaps I'm selling that part of the story short.

The English dub for this film is provided by Bang Zoom rather than Funimation, which means that Wendee Lee is playing Conan, Cristina Vee is Ran, and Lucien Dodge is Heiji. Dodge in particular does an excellent job with delivery, but the whole cast is very strong. The dub also uses the original Japanese names for the characters (Ran not Rachel, etc.), which feels like a particularly good choice for this film since it is set around the uniquely Japanese game of karuta. No one does any accents like you sometimes see and hear for Osaka/Kyoto-based characters, although it is worth noting that Heiji's mother and Momiji do speak using a more extensive and formal vocabulary than the characters who are visiting the region.

Art for the film is a bit of a mixed bag, mostly because Gōshō Aoyama's original character designs have some idiosyncrasies that don't always animate well, like the pointed snouty noses or the huge heads on some of the kids. (And Ran's hair cone, although at this stage of the game it's probably time for me to get over that.) But the use of maple leaves and color is striking (down to Momiji's special manicure), the cards are beautifully rendered, and there's a real sense of closeness and danger to scenes where characters are directly threatened by smoke and flames. The animation is also beautiful, with moments like Ran catching a fainting Kazuha standing out in their smoothness and fluidity. Music isn't particularly striking, but the ending theme is definitely pleasant.

The Crimson Love Letter is an all-around enjoyable film. The mystery is interesting and fair play, the characters' interactions are fun, and the whole thing is very nice to look at. While you'll get more out of it if you're familiar with the franchise (a bit of summary is provided for those who aren't, but it really isn't enough) and, to a lesser degree, karuta, this is a nice way to spend two hours figuring out a crime alongside one of anime's most enduring detectives.