“The summit is somewhere up there,” says Mr Steven Yeun, waving a finger. “It’s shrouded.” He is gesturing towards Jones Peak in the San Gabriel Mountains, northeast of Los Angeles, which is wrapped in wispy clouds on this spring Sunday morning.

We walk past a wooded glade where an Alcoholics Anonymous meeting is in progress. To the side of the trailhead before us, an elderly couple wrapped up in padded jackets arrange an elaborate picnic spread of homemade dim sum on a blanket. The setting, near Yeun’s home, is a reminder that much of Los Angeles is far from the bright lights of Hollywood and sun-kissed scenes in Mr David Hockney paintings. The actor, who has spent the past five years climbing towards a hazy shade of stardom, surveys the trail map and selects a winding route to the obscured mountain top.

Yeun, 38, is dressed in a blue-grey sweatshirt, black workout trousers and worn adidas hiking shoes. His cropped hair went unstyled this morning. He’s filming in Los Angeles for the first time. It’s been a challenge to shift mental gears to be fully present with his wife and two children each night. “I think I’m getting the hang of it,” he says. “Work always reflects for me on a personal level. Can I come in and out of my mind of my own will, instead of being run by my mind?”

It seems almost ironic that the deeply introspective and humanistic Yeun rose to fame as a post-apocalyptic action star in The Walking Dead. He has spent the years since he left the show delving into thoughtful projects that have brought him acclaim, the admiration of auteurs and a historic Academy Award nomination (the first Asian-American up for Best Actor). Despite being maniacally selective and working outside mainstream Hollywood, he may be on the path to becoming a generational actor, but he is only ever trying to find a way out of his own head.

“I don’t know if I have any wisdom,” says Yeun. “But I’ve learnt that your thoughts are not who you are. I used to let thoughts turn into feelings out of my control. These days, I’m a little bit more aware.”

The comment hangs in the air for a moment and he slowly starts up the tree-lined trail. “Should we start off?”

As we begin snaking uphill, Yeun turns to his next film, Mr Jordan Peele’s Nope. Like Peele’s earlier features, Get Out and Us, the film employs horror tropes while pushing the genre’s boundaries. Its plot is guarded like a state secret. Yeun repeatedly apologises for the need to be tight lipped (“So sorry.” “I wish I could talk to you about it.” “I don’t know what I can say that won’t spoil things.”). The film involves mysterious disappearances and at least the appearance of an alien invasion. Online speculation suggests the title is an acronym for Not Of Planet Earth. What is clear is that Nope will be a big summer movie and Yeun will be a big part of it.

According to Peele, Yeun’s character is “pivotal” and “embodies one of the central themes in the film and he pulls it off brilliantly”. Once Yeun signed on, he helped Peele reshape the role. “Jordan gave me a lot of space to re-excavate this character,” the actor says. “We needed to take some time to tailor it, to be an individualised three-dimensional character.”

All we know about Yeun’s character is what we glimpse in the trailer. He stands in a horse show ring, wearing a bright red suit, bolo tie and cowboy hat. “What’s interesting about a hat and a bolo tie, all those things, is they can also be masks and I’ve always been fascinated with that – a character’s mask,” says Yeun. “He’s someone else underneath all that. So am I.”

Born Yeun Sang-yeop in Seoul, South Korea, Yeun moved with his family at the age of four, first to Saskatchewan in Canada, then to Troy, Michigan, in the Detroit suburbs, where he started to become Steven (after a doctor whose name his parents liked). After getting a guitar as a teen, he came out of his shell and became the bandleader of the local Korean church’s praise team. He performed a cover of Incubus’ “Drive” at the church talent show. At college, he majored in psychology with a concentration on neuroscience, on a path towards medical school. He watched and later joined the school’s improv comedy troupe. After graduating, Yeun moved to Chicago and began performing in Stir Friday Night, an Asian-American comedy group. Eventually, he landed a coveted place in The Second City, the company that launched Mr John Belushi, Mr Dan Aykroyd, Ms Gilda Radner and, more recently, Ms Tina Fey, Ms Amy Poehler, Mr Stephen Colbert and Peele.

Yeun yearned to act on stage, but was never considered for substantial parts. Many of the roles he was sent were updated versions of the notoriously racist caricature Long Duk Dong from Sixteen Candles. At one point, Yeun went to an audition for The Awesome 80s Prom, a Tony N’ Tina’s Wedding-esque interactive show, prepared with a monologue from Ferris Bueller’s Day Off. He quickly realised he’d been earmarked for the part of foreign exchange student Feung Schwey when he was asked to deliver his lines “in an accent”. In a sense, comedy became a salve for Yeun’s wounds.

“I need to diffuse or deflect that disappointment through the skill I had, which was to make people laugh,” he says. “And when I got into comedy, I deeply enjoyed it.”

Yeun moved to Los Angeles in 2009 and quickly landed a guest spot on The Big Bang Theory. Less than six months later, his career took a dramatic turn. He auditioned for a new TV adaptation of The Walking Dead comic-book series and landed the part of Glenn Rhee, a wayward pizza delivery guy who finds direction in the face of the zombie apocalypse. For six seasons, Yeun was a fan favourite and, according to showrunner Mr Glen Mazzara, “the heart” of one of the most successful series in television history.

Yeun loved his time on the show, but it came with a heavy burden. His on-screen interracial relationship and his badass zombie-slaying ways made him a visible avatar of Asian masculinity.

“I felt the weight of all that, acutely at times,” he says. “I’ve since realised that once you help break through a construct, there’s a gang load of people right behind you ready to lay the foundation. So it’s not on me to lay more bricks; it’s just to get out the way.” He did that when Glenn met a brutal end in the premiere of season seven.

Killed off in a zombie show, Yeun resurrected himself slowly and methodically. He eschewed the mainstream TV and film opportunities teed up for him. “I think a lot of people wanted me to strike while the iron was hot and I probably looked foolish for not striking when the iron was hot,” he says of his 2016 departure from the series that made him a star. “But I will say the doors that were open had been opened before. They weren’t brand new.”

Going somewhere new began with a return to the country of his birth. Anticipating his exit from The Walking Dead, Yeun had visited South Korea and met a series of notable directors, including Messrs Bong Joon-ho and Park Chan-wook. Nearly two years later, Yeun received an unexpected email from Bong saying he’d written a part specifically for him – an animal rights extremist known as K in his film Okja (2017). Yeun followed that with meaty roles in Mr Boots Riley’s Sorry To Bother You and Mr Lee Chang-dong’s Burning.

Yeun’s dramatic transformation picked up speed with Minari, writer-director Mr Lee Isaac Chung’s semi-autobiographical tale of a Korean family trying to put down roots in rural Arkansas. Yeun, an executive producer on the film, plays Jacob, a determined father who dreams of establishing a farm but finds himself at war with a strange, inhospitable land. The performance brought Yeun his Academy Award nomination (the film earned six nominations, including Best Picture), but Oscar nods, as we know, do not cure all ills.

“I still get offered roles that may be more colourblind,” he says. “But the role itself always feels like it misses me. I don’t feel like I’m cast for me. I’m getting cast still as an Asian person, just a 2.0 or 3.0 version.”

That wasn’t the case with Beef, the limited series he’s now filming with Ms Ali Wong about a couple who can’t let go of a road-rage incident. And it certainly wasn’t the case with his role in Nope. “It’ll be something new,” he says. “Jordan’s not just content with making representational films. He’s trying to make cinema that’s never been seen before.”

Peele had previously cast Yeun in an episode of The Twilight Zone and knew his strengths. “What he does with all of his roles is incredibly precise and sharp,” says Peele. “He also brings real, grounded humanity to his work.”

Still, Yeun surprised the director. In one scene, co-star Ms Keke Palmer improvised a line and referenced a poster on the wall. “Without hesitation, Steven responded with intimate details – only knowable to me and him from a conversation long ago – about it,” says Peele. “That underscored just how deeply he invests in his preparation. As a director, moments like that make you aware there are levels going on underneath a character that even you aren’t privy to.”

As a family of hikers pass to our left, Yeun chooses the narrower, less-trafficked trail spur to the right. It spits us out on a promontory with a bench that overlooks much of the Los Angeles Basin. While the summit is still socked in, Yeun and I take in the view from our perch. After a few minutes, he says, “There’s a power to accepting that you’re floating and that there’s no place for you to land yet.”

As we start back down the mountain, a passing hiker identifies Yeun as “that guy from The Walking Dead” and asks for a selfie. Later, Yeun calls the series something beautiful that served him well, but which he had to leave behind. It will not be the last.

“I’ve been thinking lately,” he says. “To cross thresholds, you have to drop all the things that got you to that point. You can’t use them anymore. And if you spent all that time carving this beautiful boat that got you to a specific destination, if you want to pass through the next door, you have to leave that boat behind.”