'I cry every time': How Kpop Demon Hunters went viral

Kpop Demon Hunters has won best animated film at the Oscars on Sunday evening - the latest in a growing list of accolades for the movie that has swept the world since it was released last summer.

At Oona Herman's elementary school in San Francisco, stickers of bright-haired characters from Kpop Demon Hunters have become the hottest currency.

Traded among students, these stickers, like so much else to do with the hit film -about a K-pop girl group using their golden voices to fight demons - are everywhere in eight-year-old Oona's life.

At Kpop Demon Hunters-themed birthday parties she attends, children get goodie bags with movie merchandise and pose for photos with giant cut-outs. Of course, they also scream along to the film's chart-topping soundtrack.

Oona cannot decide what she likes most about Kpop Demon Hunters, so she declares: "The characters, and all the dance moves and songs!"

Since its release on Netflix last summer, Kpop Demon Hunters has earned recognition on the biggest stages. It won the Golden Globe for best animated feature and best original song; became the first-ever K-pop song to win a Grammy; it was nominated for two Oscars on Sunday and has already won one.

The film's virality has taken the world by surprise - and its creators too.

So much so that when the film blew up, fans lamented over the lack of merchandise. Netflix told Hollywood Reporter that its pitch for merch ahead of the release drew only "soft" interest from retailers. Now companies are racing to get those toys on the shelves.

But Oona and her friends aren't the only ones under the spell of the demon-busting crooners. Her mother, Christine Kao, was surprised by how much she enjoyed it too.

"When we're watching it, I really cry every time," she tells the BBC.

"Oona's always like, 'Why are you crying?' I was like, 'Because it's so beautiful! I think that caught on to a lot of adults unexpectedly."

If you haven't watched Kpop Demon Hunters, the below sections contain spoilers.

How it's done, done, done

In the film, the protagonist Rumi finds herself torn between her responsibility as a demon hunter and her secret identity as a half-demon.

For Christine, this tension strikes a personal note.

"Just seeing an Asian American, her struggle with her family and expectation, there's a lot of identifiers there that we take with us," Christine says. "We didn't have something like this when we were children."

Of course, beyond the movie's fandom, this universal tale about self-acceptance comes in the form of a love letter to K-pop.

For Oona, the Saja Boys - the supernatural boy band in Kpop Demon Hunters - remind her of her favourite K-pop band BTS, "because they all look a little bit different and they always change their looks".

Indeed, Soda Pop, the bubblegum hit by the Saja Boys, has been widely compared to BTS' Butter.

There are also plenty of satirical easter eggs for K-pop fans: a furtive conversation between two idols immediately sparks dating rumours; the debut of a new band quickly sucks fans away; and they swoon over male idols for their "respectful" behaviour.

"It's really funny if you're a K-pop fan, there's a lot of inside jokes," says Dr Grace Kao, Oona's aunt and a sociology professor and K-pop researcher at Yale University.

"But if you're not a K-pop fan, you don't really need to get those jokes to enjoy it."

Plot aside, the movie has opened a can of earworms that have dominated film festivals, music awards and the background score in malls around the world.

Oona says even her friends who haven't watched the movie "know all the songs".

The team behind the award-winning soundtrack include both K-pop and Hollywood-trained songwriters and producers.

So it's little surprise that the soundtrack of Kpop Demon Hunters sits at a clever intersection between K-pop and Western pop music, says Ray Seol, associate professor at Berklee College of Music.

The producers "were very smart making this more global sound", he tells the BBC. "So the general audience, when they hear this music, it is still K-pop but somehow it's really similar to the pop music they are familiar with."

While most K-pop tracks are dance music with catchy lyrics, in Kpop Demon Hunters the songs serve to propel the story. Also setting the songs apart are the lyrics, which have "deep meaning of findings themselves, and about their identity", Seol says.

"The worst of what I came from, patterns I'm ashamed of," Rumi sings in What It Sounds Like - at one level, it is a reference to the marks on her skin, which give away her part-demon heritage, but what resonates is the scars she is trying to overcome.

Finally, Kpop Demon Hunters comes at a time when global appetite for Korean pop culture is expanding.

"I feel like it's not only the quality of the animation itself," Seol says. "It is time the world is ready to see this very authentic animation, and it's very fresh."

The genre has come a long way since Gangnam Style, the viral Korean track that shattered cultural barriers and YouTube viewing records in 2012.

Today, bands like BTS and Blackpink have become regular attendees of Western awards shows, newer groups like Stray Kids and NewJeans increasingly boast members of diverse nationalities, South Korean president Lee Jae Myung has embraced K-pop as a soft power tool to drive diplomacy and economic growth.

One of them is Yenna Oh, an elementary school student in Paju city, near Seoul. She has amassed a photo card collection of the movie's characters, which she has gingerly filed in an album.

"I especially get excited when Rumi, Mira, and Zoey defeat the monsters," says the eight-year-old.

What adults see, though, is a new swell of the unstoppable Korean Wave that is sweeping the world.

"I think [Kpop Demon Hunters] marks a turning point in terms of how cool Korea is," says Kao, the Yale professor.

"I don't think it's just K-pop, but just sort of K-everything."

Additional reporting by David Oh in Seoul