K-pop's famed sibling duo AKMU returned Monday with a new single "Love Lee," bringing back the pair's trademark positive, upbeat energy.

The co-ed duet, consisting of Lee Chan-hyuk and his younger sister Lee Su-hyun, will drop its fourth single, "Love Lee," Monday evening, marking the first comeback in over two years since releasing its collaboration album, "Next Episode," in July 2021.

During a press conference held in Seoul on Monday, the siblings introduced their new single, a two-track package comprising two songs, "Love Lee" and "Fry's Dream." The single captures the duo's cheerful and buoyant spirit, reviving it from some of the pair's earlier works.

According to Chan-hyuk, the new song, "Love Lee," can be seen as the second edition of the band's debut title song, "200%."

"With '200%,' We sang with a naivety, unaware of what the public wanted from us. We put ourselves out there and sang what we wanted with confidence. Since then, we've explored different genres, and now I think we know a tad better about what people expect from us. 'Love Lee' is a song that we wrote as a gift for them," said Chan-hyuk, the song's main composer and sole lyricist.

The act's turn of direction favors Soo-hyun, who endured years of her brother's highly experimental zeal.

"As our time as AKMU passed, it became too much for me to handle my brother's colors," Su-hyun said, laughing, but with serious undertones.

"After 'Nakka' ... I told him that I will not take on any more challenges. I want to go back to 10 years ago, I said. I wanted to make music like '200%,' carefree and easy on the ears," Su-hyun said. "Nakka" is the lead song of the band's last album, "Next Episode."

Debuting in 2014 with its first LP "Play," fronted by "200%" and "Give Love," AKMU has walked a prominent path in the local music scene as a self-produced sibling duo. With Chan-hyuk as the creative brain and Su-hyun, his vocal muse, the duet delved into a niche corner of the music scene, experimenting with unconventional melodies and playful lyrics that could only be defined by themselves.

The more fame AKMU's music garnered, the more Su-hyun seemed to lose her glitz, Chan-hyuk recollected.

"I realized that I've been doing only what I wanted to do for a long time as I watched how happy Su-hyun was working on this album. Looking back, it was around (the making of) 'Dinosaur' that she seemed to find singing less enjoyable. I didn't realize it then. It sunk in gradually as I saw Su-hyun having less fun making music," he said.

When writing and composing "Love Lee," Chan-hyuk tried his best to take all of his sister's opinions on board, making an effort to place her in the spotlight.

"I feel like it's our new start. It's the first time where he made an album conforming to my needs. He wasn't so confident about it all but constantly asked me what I wanted. He even took the guitar and his laptop on our family trip and continued working there," she said, adding that she feels highly content with the outcome.

Ten years ago, AKMU simply asked to "Give Love" with its 2014 song. They were young and innocent, Su-hyun recollected, adding, with "Love Lee," they have another go at the romantic serenade, this time, in a more refined manner.

The title "Love Lee" comes from "lovely," a word that Chan-hyuk had become attached to in recent months.

"When I was in the UK, people there always said 'lovely,' and it sounded pleasant yet sophisticated, and it stayed in my mind for a while," he said.

"Lovely" was the perfect term to describe their new anthem of love, he thought. By replacing "-ly" with "Lee," he gave it two meanings: a sweet proposal of love for Lee, an unidentified recipient of love, and an invitation of love for the Lee siblings.

"Fry's Dream," the second song of the new single, also takes the duo back 10 years. The song was first unveiled at the duet's first concert held in 2014. Before it could see the light of day, Chan-hyuk gifted the song to the duet's close friend and fellow singer-songwriter IU, who recently re-gifted it to Su-hyun.

Su-hyun, who Chan-hyuk said is the exact manifestation of the slow-paced and relaxed life described in "Fry's Dream," created the animation illustration for the song's lyrics video.

The siblings said their fourth single, "Love Lee," could be seen as the new start to AKMU's career.

"I realized that AKMU's music should be about what both of us enjoy. This hit me even harder after I (started doing the music I wanted to do) last year," said Chan-hyuk, referring to his solo debut with his first LP, "Error," in October.

While the two may appear to be quite laid back in how they treat one another, Chan-hyuk and Su-hyun said Monday they've come to appreciate each other as teammates more.

"I think the greatest part of (a sibling group) is that you tackle everything with someone who is closer to you than anyone. The biggest merit is that our lives go along with our music," Su-hyun said.

Indeed, it was Chan-hyuk who stood by -- and still stands by -- Su-hyun during the darkest time of her life.

"I said in a TV show that I was having a hard time. ... To be honest, I'm still in the process of overcoming it, and my brother stood by me, offering support and advice and expressing his wish for me to discover the joy and fun of making music when making this album," said the 24-year-old singer.

"I think Su-hyun became troubled by thoughts about music because I burdened her with the ideas that I wanted to portray with our music. I realized that too late and I believe it's in some part my responsibility that Su-hyun is (having a hard time)," Chan-hyuk said, adding this has given him perspective on AKMU's direction.

"It became clear that, as AKMU, we have to work together on finding what the public wants from us. ... I now have my solo music and other individual projects to express myself, so AKMU's music can now be reserved just for our fans," he said.

AKMU will mark its 10th anniversary in April, and the new single is the first part of the celebration, Su-hyun added.

Having worked apart for two years, the siblings said they will be focusing on activities they could do together over the coming days.

Among their new projects is the popular KBS 2TV music talk show, "The Seasons," which they will co-host. They are the new emcees of the TV program's third season, which is set to begin airing on Sept. 1.

"This is our first time hosting something together. One very calm person and another very atypical person will be joining hands, joined by a new guest every episode. We'll need to work together as a team," Su-hyun said.

Chan-hyuk added, "As we have very different personalities ... the range of guests we can host are different. I anticipate a great synergy from that. It will be a good opportunity for us."

The pair also announced that a concert series is upcoming.

"We'll be launching our first concert for the first time in three years. I hope you guys will like it," Chan-hyuk said, to which Su-hyun added, hinting of a tour, "We'll be meeting audiences across various regions."