Sony PicturesIt’s easy to joke about two Americas nowadays, especially when coming face-to-face with a global phenomenon that’s taken the world by storm right under your nose. Demon Slayer is one such anomaly: the beloved anime has amassed a loyal, passionate fan base in what feels like record time. It’s also already broken a major box office record with its first big-screen film, Mugen Train, which beat out Studio Ghibli’s Spirited Away to become the highest-grossing movie of 2020. Five years later, the franchise has yet another record. Its latest film — which goes by the mouthful of a title Demon Slayer: Kimetsu no Yaiba – The Movie: Infinity Castle — Part 1: Akaza Returns (yes, really) — now ranks as the highest-grossing anime film in the U.S., pulling in a shocking $70.6 million in its opening weekend.Infinity Castle’s wild success might seem to come out of nowhere, at least for those who’ve never heard the words “Demon Slayer” in their lives. In truth, though, the anime series has earned every bit of its status as a phenomenon. What exactly is Demon Slayer?Part of Demon Slayer’s popularity comes with the simplicity of its premise. Like every shonen, it follows the adventures of a young man destined for greatness. Tanjiro Kamado once lived a peaceful life with his mother and siblings, but in his world, such peace is always fleeting: demons roam the wilderness at night, devouring any human caught unawares. Tanjiro returns home one morning to find his entire family slaughtered — all save his younger sister, Nezuko. Unfortunately, she’s been turned into a demon (the fiends in this universe function kind of like vampires, transforming humans with their blood), but is somehow rejecting the transformation. There’s still a shred of her humanity left, and Tanjiro, optimist that he is, is determined to change her back into a human. With Nezuko in tow, Tanjiro sets off to join the Demon Slayer Corps, a group of warriors who — you guessed it — hunt demons and might have the answers he seeks. So begins one of the most compelling anime series in years: Demon Slayer moves at a brisk pace, but it always earns its crowd-pleasing moments. As Tanjiro levels up, so too does Nezuko, unlocking new demon powers to assist her brother in battle. And the battles are always breathtaking — anime studio Ufotable consistently pulls out all the stops, rendering creator Koyoharu Gotouge’s original manga in vivid, visceral color. It also doesn’t hurt that Demon Slayer is impossibly earnest. While edgier anime like Jujutsu Kaisen and Chainsaw Man hold down one corner of the market, Demon Slayer — though violent enough to earn an R-rating — courts four-quadrant appeal. Throw in a batch of personable, fully realized characters and an ingenious, ever-evolving story, and it’s easy to see how the series has garnered such a large, passionate fanbase.Why is Infinity Castle so popular?Infinity Castle is the beginning of the end for Demon Slayer. | Sony Pictures Animation Infinity Castle is essentially the Avengers: Infinity War of the Demon Slayer saga. The film is the first installment in a three-part feature-length finale for the entire series. Demon Slayer is in the endgame now: Tanjiro and his allies in the Corps are closer than ever to defeating their Big Bad, head demon Muzan Kibutsuji. The only problem is, they’re now trapped in his sprawling lair, an expanse of ever-changing rooms called the Infinity Castle. Our heroes are scattered to the winds, but Infinity Castle mostly follows Tanjiro and his mentor, Tomioka Giyū, as they face off against a ruthless upper-level demon, Akaza. (This is also technically a rematch for Tanjiro, as Akaza murdered someone close to him in the last Demon Slayer movie, Mugen Train — hence the subtitle “Akaza Returns.”)Audiences came out for Infinity Castle because this is the beginning of the end. It’s not uncommon for whole anime seasons to be repackaged as feature films — Mugen Train was later extended and cut up into separate episodes, marking the official beginning of Demon Slayer Season 2. Unlike Mugen Train, though, Infinity Castle and its sequels will only live on as movies. They’re also designed to be seen on the big screen: sure, they’ll eventually be available to stream on Crunchyroll, but Ufotable goes all out with Infinity Castle, delivering the kind of visuals that more than justify this jump to theaters. The film’s success comes at the tail of a perfect storm, from Demon Slayer’s built-in fanbase to the hype behind its previous installments and the dearth of animated films currently in theaters. The anime may not land on a novice’s radar, but it’s more than earned its success; even if Demon Slayer is coming to an end, Infinity Castle and its sequels will ensure it does so with a bang.Demon Slayer: Kimetsu no Yaiba – The Movie: Infinity Castle is now playing in theaters.