The shimmer of youth fades ever so fast that, even when standing at its center, we often feel overwhelmed by the fear that it might slip through our fingers in no time.

Perhaps now is that shining moment for the five members of boy band Tomorrow X Together, also called TXT for short.

“Our spring began and our youth bloomed on March 4, when Tomorrow X Together met Moa,” Soobin, the leader of the quintet, said on Sunday during the act‘s concert. Moa is the collective name for TXT’s global fanbase.

Soobin‘s heartfelt confession came after the band’s performance of its upcoming song, “Blue Spring,” during the act‘s second day of its new world tour, “Act: Sweet Mirage,” held in Seoul.

An unreleased song presented as a gift for fans coming to the concerts, “Blue Spring” is a self-written song by the five members.

“The five of us wrote the lyrics together thinking of the moment when our frozen hearts and worries all melted down after we met Moa,” Soobin said about the song.

The song was introduced for the first time during the two days of Seoul concerts in the act‘s world tour, “Act: Sweet Mirage,” which kicked off on Saturday at KSPO Dome in Olympic Park, Songpa.

During a press conference about the world tour conducted ahead of Sunday‘s show, Beomgyu, who took part in the composition of the acoustic ballad score, said, “We made the song as a gift for Moa. It carries a message about the time we spent together as trainees since we first met each other and how much we value Moa.”

Indeed, the two nights of “Act: Sweet Mirage” at KSPO Dome were like an incarnation of the team‘s remarkable growth, which they have seen over the past years since their debut in 2019.

In July 2022, the five-piece group kicked off its first world tour series, “Act: Love Sick,” in Seoul‘s Jamsil Arena, a venue half the size of the 10,000-capacity venue where the boys began their second world tour over the weekend.

The beefing up of the venue size itself is worth applauding, but after watching Sunday‘s show, the enhancement in the concert’s quality and the perfection -- to which it was evident the members had striven for -- were almost breathtaking.

The magic began the instant the show kicked off with the night‘s opener, “Blue Hour.” As the members appeared onto the stage spruced up in elaborate dark-green uniforms, a sweet, savory scent spread through the air, captivating the nose through the next track, “Can’t We Just Leave The Monster Alive?.”

“This tour will linger with you guys for long. To do that, we prepared the fragrance during ‘Blue Hour.’ We made it ourselves,” Taehyun said, to which Beomgyu chimed into say, “Don‘t miss out on the sweet mirage we’ll be showing through today‘s concert!”

The bandmates took off their uniforms on the stage and jumped straight into the next songs, “Drama,” “No Rules” and “Cat & Dog.” As the bandmates jumped around the expansive stage, the fans responded by belting out screams to their every move.

Up next was a non-stop flow through what Taehyun put as “eight songs that follow from TXT‘s redemption to despair.”

Kicking off with Hueningkai‘s solo dance break during “Run Away,” the section ran through a string of the act’s biggest hits, “We Lost Summer,” “Can‘t You See Me,” an emocore mix of “0X1=LOVESONG (I Know I Love You),” “Dear Sputnik” and “Magic,” before closing with special solo and unit performances in “Opening Sequence.”

Sunday's concert was more than a live music show. The show made full use of the instruments and structures inside the dome to turn the gig into a splendid festival festooned by colorful confetti, bursts of fire, graphics on screens and impressive teamwork between the members, the dancers and the whole team behind.

Tempering down on the tone with ballad renditions of "Anti-Romantic" and "Eternally," the boys upped the beat again with "Good Boy Gone Bad," "Tinnitus," "Angel of Devil" and "Ice Cream."

What stood out the most during the new world tour was the five members‘ ability to communicate with the audience. While there were still moments when the boys seemed to be reading off a script, even those awkward sentences all seemed to end in blurts of spontaneous remarks from the members.

This connection with fans was most evident during the “Happy Fools” challenge moment. The members taught the audience a short part from the song‘s choreography on the spot and each took the helm of commanding a segment of the crowd. Among them was Bang Si-hyuk, the founder and chairman of the group’s company, Hybe, who induced huge laughter from fans and members by dancing to “Happy Fools” alone from his seat.

Ending the night were "Sugar Rush Ride," the title track of the latest album, "The Name Chapter: Temptation," and three encore songs: "Farewell, Neverland," "Blue Spring" and "Our Summer."

TXT explained it is significant that they had placed "Farewell, Neverland" as the last track off its latest album, among the end songs.

“The album deals with the small and big temptations that we could fall for in life. We especially treasure ‘Farewell, Neverland’ because it gives a big hint about our next album, which we are currently working on,” Taehyun had said during the press conference on Sunday.

The story resembles TXT‘s own path until now. Many temptations trying to thwart them on their path to stardom have existed, but the five members have endured and overcome them to stand where they are now.

With “Blue Spring,” the members reflect upon the times in which they have striven together and the value of their fans, Moa, who appeared in front of them, rewarding them for their efforts.

"There were moments when people used to ignore us, saying we'll waste our youth. But here I am, performing in front of 10,000 Moa. What can be called a more beautiful youth than this?" Yeonjun said through tears.

"I have a goal with this tour. I hope that by the end of the tour, we can sing along to 'Blue Spring' again with Moa," Beomgyu said.

With eyes glistening and his voice tense with excitement, Hueningkai said, "It's a treasure, this moment, I feel like I've lived for it. I'm rejoicing since I so badly wanted to stand on this stage. I felt grateful even as I was performing on the stage. It was also nice to hear your voices up close. Thank you for making my youth."

Promising to come back soon, the five members wrapped up the night with "Our Summer."

With "Act: Sweet Mirage," TXT is now set to travel around 13 cities in Asia and the US, where they are now planned to hold 23 shows. Starting with the Singapore concert on April 1, the tour will run through until May.

In August, the quintet is set to headline American music festival Lollapalooza, set to take place in Chicago.