When the actress Karen Fukuhara was shooting Suicide Squad in Toronto last year, she befriended a stuntwoman who happened to be working on another film across town. Whatever that production was, Fukuhara can no longer recall, but it is assuredly not causing as much blockbuster noise as the lustily deranged comic-book tentpole that has been hotly anticipated since it was announced as DC's answer to Marvel's Avengers franchise in 2014. "My friend was filming a couple of miles away," Fukuhara, 24, recalled, "and she told me they had to stop for hours because the sound of our ammo firing traveled all the way over to their set."

These days, superhero franchises are where movie stars go to burnish their value—and Suicide Squad, out August 5, has plenty of wattage, with Margot Robbie, Will Smith, Jared Leto, Ben Affleck, and Cara Delevingne as Squad members. But Fukuhara is a complete unknown—Katana, the masked, blade-carrying mystery warrior who protects the Squad (the part is no mere cameo), is her first onscreen role. In anything.

"It's very surreal," Fukuhara said. "In the past year, my life has changed so much."

Growing up in Los Angeles, she had always been been enamored by the movie industry. In middle school, she landed a gig through a friend hosting a show on Disney, in which she interviewed the cast of Disney movies, like Johnny Depp during the height of the Pirates of the Caribbean years. But she found it hard to break through as an actress. "Coming from a first-generation immigrant family, we just didn't know how to go about the business," said Fukuhara, who is Japanese-American. "We didn't even know what an agent was."

She still didn't have an agent when she got the call to audition for Suicide Squad, only a manager. No doubt it was her martial arts training—and director David Ayers's decision to actually hire an Asian actress to play a Japanese character (whew)—that helped her land her breakthrough role. In high school, Fukuhara was a karate champion. "I only got into it because my little brother started karate, and my mother wanted me to babysit him," she explained. "He was a troublemaker in class—and thank god for that now."

As Katana, Fukuhara did all of own stunts save one—"I even ran on top of a car in the pouring rain," she said—and mastered the art of swordfighting at least to the extent that she wouldn't, say, accidentally take off Margot Robbie's head with an errant swing of the blade. "Margot's very tough, but yeah that would've been bad."

For a newcomer on the set of a movie rumored to have cost upwards of $150 million, the pressure to perform must've been enormous, but the mood was loosened up by the likes of Robbie (who plays Harley Quinn, the Joker's equally maniacal sidekick) and Will Smith (who plays the assassin Deadshot). "Will set the family vibe on the film," Fukuhara said. "He created this gym on set so we could train when we weren't shooting. And he would bring coffee and snack trucks to set."

And of course there was Jared Leto, whose gossiped-about antics on set (his gifts to his co-stars have included real bullets and a dead rat) are likely tied to his method approach to playing The Joker, a role with Heath Ledger-sized shoes to fill. As it turns out, his commitment was as total as the rumors have suggested. "To be honest, I didn't meet Jared until Comic Con this year," Fukuhara said. "Because every time I saw him on set he introduced himself as the Joker! I would try to say hi to him as Karen, and he would come at me with full Joker."

She laughed.

"It was weird every single time."

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