At 9:30 a.m. on a Thursday, the Harrys began to arrive at Beachwood Cafe. Young women with neon hair extensions, colorful crocheted cardigans and shirts illustrated with cherries, sunflowers and the word “Pleasing” piled out of rental cars and Ubers. They were trailed by their mothers and filming on their phones. By 10:30, the mom-and pop eatery, which has been around since the 1970s in the heart of Beachwood Canyon, Los Angeles, had a 30-minute wait, and a swarm of teenage girls taking photos in front of its blue door.

Who are the Harrys? They are Harry Styles superfans, and hordes of them have been making the pilgrimage to Beachwood Cafe, a cheerful spot with an all-day menu off a small village square, since December 2019. That’s when the superstar briefly name-checked the restaurant in the song “Falling”: “And the coffee’s out at the Beachwood Cafe,” he sang. That one line — which Styles-olgoists believe to be about his ex Camille Rowe, a former Beachwood Canyon resident — sent a bat signal.

“I just felt like coming here would complete the whole Harry Styles experience,” said Caysey Gossweiler, 27, who traveled from Maryland to attend one of the three concerts that Mr. Styles would perform at the Kia Forum that weekend in late January.

“It’s panic-inducing; I could literally evaporate thinking about it,” said Noelle Jay, 26, of being in the same space where Mr. Styles once ate eggs. “He’s like a god,” added her cousin Mia Tucci, 17, whose hair was a shade of Kelly green. “He’s like my comfort person, my light, my inspiration, all of the above,” Ms. Jay replied.

Nearby, Nathan Freeman, 26, and his wife, Shannon Freeman, 25, were taking photos of Taylor Anderson and Alyson Johnston — 20-year-old college students from Oregon they had just met. “It was like — where should we go for breakfast? Harry told us where to go!” Mr. Freeman said gleefully.

The couple, who wore matching crop top and bell bottom ensembles to attend the concert at the Forum, had spent the previous day at Sycamore Cove Beach in Malibu, where fans say Mr. Styles filmed the videos for “Watermelon Sugar” and the One Direction song “What Makes You Beautiful.”

“She ran and screamed and fan-girled,” Mr. Freeman said, describing his wife’s behavior upon arriving at the beach. “I was like, ah!” he shrieked. “I love this for you!”

Ms. Freeman said she admired Mr. Styles for his kindness. “I’ve never seen a scandal from him ever — which is amazing.”

Over avocado toast at a table inside, Ms. Anderson — who made her family do a detour during an Amalfi Coast vacation to visit a street where Mr. Styles filmed parts of the “Golden” music video (she found the location by searching Google Maps for landmarks in the background of the behind-the-scenes video) — offered her perspective on the fandom. “It’s a family in a lot of ways,” she said. “A good example of how the online world connects people.”

Ms. Johnston finished watching a video on her phone of Mr. Styles doing Pilates, via the fan account Harry Florals, and added: “You can just kind of look at someone, and if they’re our age and wearing clothes that resemble the Harry style it’s like, OK, these are people you can talk to who are nice.”

“The term is ‘Harry coded,’” explained Xoee Margolis, 26, who was wearing neon orange Adidas Gazelles (inspired by ones Mr. Styles wears from the Gucci/Adidas collaboration). She held two new Beachwood Market totes in her hand, which she’d seen while browsing the cafe’s merch section online from her home in New York City. “Wearing a little cherry is an ode to the ‘Cherry’ song, carrying around a Beachwood bag the shoes are Harry-coded — it’s a vibe.”

“I made the mistake of not bringing in merch earlier,” said the cafe’s owner, Mike Fahim. But when he discovered eBay and Etsy accounts selling knockoff merchandise for his restaurant, he saw a business opportunity.

When Mr. Fahim took over the cafe in the fall of 2019, the crowd was a mix of locals, tourists headed to the nearby Hollywood sign, business lunches from film studios, and celebrities flying under the radar. In early 2020, the clientele started shifting to Gen Z girls and young women — some of whom bring cardboard cutouts of Styles for photos — and, in some cases, their parents.

Mr. Fahim, who had never heard of Harry Styles, embraced the affiliation.

Now, the tip jar says “Harry Tips Here.” A sign depicted in a mural declares “The Coffee’s Out,” referring to the line in the song featuring Beachwood. And he and his staff are happy to take photos and answer fans’ questions about what Mr. Styles is said to have eaten (the Beachwood Scramble), and where he sat (the table at the center of the room, and the booth in the far right corner). Someone on the staff monitors “the whole situation on Instagram and TikTok,” Mr. Fahim said. If Mr. Styles is in town — as he was for two weeks in the fall, when the cafe ran out of menu items and merchandise — they double up on staff and supplies.

On the Saturday of Mr. Styles’s concert run at the Forum, a line started forming outside of the cafe an hour before opening. It included Emma Szumowski, 21, from Massachusetts, who stood with her parents, Laura and Steve McMahon. The concert she’d gone to the previous evening was her sixth time seeing Mr. Styles. She had tickets for one more show in Los Angeles and two in Palm Springs that week.

“I get it, I’m a big Springsteen fan — I started following him around in ’84,” said Mr. McMahon, 58, who, at his daughter’s request, had gotten up early to be second in line.

The line snaked past the dry cleaners and into the square. At 8:40 a.m., Nicholas Braun, the actor who plays Cousin Greg on “Succession,” joined it — appearing slightly bewildered by the crowd — and then left before he was seated.

Across the street, Jim Krantz, 67, and Brian Burchfield, 59, Beachwood Canyon residents, stood outside the Hollywoodland Realty building, taking in the scene.

“I mean, this was like ‘Mayberry R.F.D.’ — but not anymore,” said Mr. Krantz, sipping a mug of tea and referencing the 1968 spinoff of “The Andy Griffith Show” — a sentence likely to draw a blank the teenage girls filming their breakfast burritos across the street.

“I think it’s fascinating, a social phenomenon,” he added. “But it’s a bit of an inconvenience when it comes to being able to do your daily life up here.”

Wait times were between two and three hours throughout the weekend. At one point on Saturday, the diners inside the cafe broke out into a loud rendition of “Falling.” Before the wave of Styles fans, Mr. Fahim typically served 300 guests from Friday to Sunday; he now serves 1,000 on average. The locals still come, but they often grumble about the wait times and lack of parking — and if they see a line, they steer clear.

Most fans agreed that this was no longer a place where Mr. Styles was likely to set foot. This realization sometimes prompted fan conspiracy theories — did he mention the cafe because he knew it would send fans flocking there, and it was too painful a place to return because of its romantic history there?

And if Mr. Styles did dine at Beachwood Cafe again, Mr. Fahim says he knows what he’d tell him: “Thank you.”