The latest to cross that threshold is NCT 127.
Nearly every patch of shade around Seoul's KSPO Dome had been claimed three hours before NCT 127 was due onstage Sunday.
Fans sat beneath trees and along concrete walls with photo cards, merchandise and lightsticks spread around them, trading collectibles and talking about favorite members while waiting for the doors to open.
The scene stretched well beyond the dome. Olympic Park was hosting three major music events on the same day, with girl group izna performing at Olympic Hall and the KB Joyolpark Festival underway at the 88 Lawn Field.
But around KSPO Dome, the green lightsticks and NCT merchandise made the destination unmistakable.
For NCT 127, the final night of its three-day Seoul run was more than another concert. It opened the group's fifth world tour, "NEO CITY : THE REDLINE," in the year of its 10th anniversary, with five members carrying a stage built around a decade of songs, choreography and an increasingly elaborate live-show identity.
A motorcycle engine roared through KSPO Dome before five figures appeared suspended above the main stage in a web of mechanical rigging.
Taeyong, Johnny, Yuta, Jaehyun and Haechan descended toward the floor as the crowd erupted.
Dressed largely in black and white, the five launched into an opening sequence driven by the hard-edged choreography and dense production that have become NCT 127 signatures over the past decade.
Fireworks burst through the opening tracks. Confetti shot across the dome by the third song. A Y-shaped stage extension pushed the performance deep into the crowd, while moving platforms and mechanical structures repeatedly reshaped the arena.
Across roughly two hours and 50 minutes, the group performed 24 songs spanning its decade-long catalog.
Newer tracks including "Legacy" and "Step Up" from the group's seventh full-length album, "BLINGY," sat alongside older staples including "Lemonade," "Simon Says," "Cherry Bomb," "2 Baddies," "Punch" and "Ay-Yo."
"Simon Says" triggered one of the loudest mass singalongs of the night, while the familiar opening of "2 Baddies" sent much of the standing section jumping.
For Park Jung-bin, a 29-year-old fan who attended all three Seoul performances, that song carried particular significance.
Park said she became a fan through NCT 127's fourth full-length album, "2 Baddies."
"I think that album shows both NCT 127's own color and its popular appeal really well," she told AJP.
She said the group's live performances were what continued to bring her back.
"The powerful choreography, the lighting and the way the whole stage is built give you so much to look at that you lose track of time," Park said.
"I never feel that an NCT 127 concert ticket is a waste of money."
The group's 10th anniversary, however, arrived under circumstances markedly different from earlier tours.
Doyoung and Jungwoo are serving their mandatory military duty, leaving five members to carry "THE REDLINE" onstage.
Rather than try to disguise their absence, Sunday's concert folded it into the anniversary narrative.
The two members appeared in prerecorded video segments, drawing immediate cheers whenever their faces returned to the giant screens.
The members also told fans that Doyoung had sent a rice-cake cake to celebrate the anniversary, prompting jokes that the show had suddenly turned into a concert where rice cakes were being handed out.
For Park, their absence gave the weekend a bittersweet edge.
"It's sad that two members couldn't participate because of military service," she said. "But luckily they appeared through videos throughout the concert."
That mixture of looking back and pressing ahead ran through the show.
Older songs were not simply pulled from storage but reworked for the new tour.
During "Cherry Bomb," Taeyong told fans that part of the performance had been rebuilt around a new bridge and rap section, recalling how he had pushed the other members to incorporate the revised choreography.
"Punch," another older track, arrived beneath a large mechanical ring descending over the stage, prompting the members to joke that the song was finally receiving the production attention it deserved.
For a group celebrating 10 years, nostalgia was present, but it rarely took over. Much of the evening was devoted instead to showing how familiar material could still be enlarged, rearranged and made to feel current.
The scale extended beyond the performance itself.
The three Seoul concerts drew about 31,500 fans in total, filling KSPO Dome across the weekend.
Some had traveled considerably farther than Seoul.
Juliana Parker, a 36-year-old teacher living in Tokyo, flew in from Japan for Sunday's finale and planned to return after the concert.
"It is always extremely hard for me to get a ticket for an NCT 127 concert," Parker said. "When the tickets open, they just disappear in front of my eyes."
When she finally managed to secure one, she booked the trip.
"So I decided to fly from Japan," she said. "It's the weekend, and I'm finally living my dream of attending an NCT 127 concert."
Parker, whose favorite member is Yuta, had brought her NCT lightstick from Japan.
The group's international reach was just as visible inside KSPO Dome.
Yuta addressed Japanese fans during the show and thanked them in Japanese, while Johnny repeatedly encouraged the crowd to stand and wave their lightsticks.
Taeyong thanked fans for spending their weekend with the group and pointed toward the next stage of the tour.
"We're starting the tour now," he said. "We'll come to see you in each country as soon as we can."
The tour then moves to Manila on Dec. 12 before continuing to Taipei on Jan. 2, Kuala Lumpur on Jan. 9 and Macau on Jan. 16.
For all the machinery, pyrotechnics and choreography, the night's most consequential number was a simple one: 10.
K-pop careers are often measured in comeback cycles, contract periods and constantly shifting generations of acts. NCT 127's anniversary gave Sunday's show a different sense of scale — not merely the launch of another tour, but a chance to take stock of a group that has stayed on the road long enough for its early hits to become nostalgia.
At one point, Taeyong asked fans to remember the occasion that way.
"When you think about our 10th anniversary, I hope this is the concert you remember," he told the crowd.
As the final Seoul night drew to a close, thousands of green lightsticks kept moving through the darkened dome a familiar sight for NCT 127, but after 10 years, one carrying a little more history than before.
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