Whether in a duo, trio, or consisting of enough members to form a mini-group from the original lineup, sub-units allow K-Pop idols to explore various genres and concepts that are different from what they’ve been doing within their collective group. Over the past decade, K-Pop has seen a surge of groups following this trend and as a result produced some of the most iconic acts and songs to come out of the genre. In this month’s History of K-Pop column, we’re taking a look into the types of sub-units that exist in this genre and how they operate—from permanent sub-units within large groups, company project groups, to temporary sub-units that are formed to await the return of some members.

The Start of the Sub-Unit Trend

In the simplest terms, a sub-unit is a smaller group formed of members from a larger group. The newly-formed mini-group will then have separate music releases and promote under the new entity. As the pioneer of the training system and dance practice videos, it’s no surprise that SM Entertainment is also the first company to debut an official sub-unit in K-Pop. The first major sub-unit to officially debut in K-Pop was Super Junior-K.R.Y. The sub-unit consists of the three main vocalists of SM’s boy group Super Junior: Kyuhyun, Ryeowook, and Yesung. They debuted in November of 2006 with an OST for the tvN drama Hyena titled “The One I Love”. Since then, the trio has released other original soundtracks for various K-Dramas including “Sky” for the drama To the Beautiful You starring labelmates f(x)’s Sulli and SHINee’s Minho. In May of 2020, the sub-unit released their first Korean album When We Were Us after having put out mostly OSTs and Japanese singles. Throughout the years, other sub-units have derived from Super Junior including Super Junior-T in 2007, Super Junior-M (Mandarin) and Super Junior-Happy in 2008, and Super Junior-D&E in 2011. With each sub-unit focusing on a different music style—Super Junior K.R.Y with R&B-style ballads, Super Junior-T specializing in Korean trot, Super Junior-Happy with bubblegum pop—Super Junior are able to explore diverse concepts with these unique member lineups.

Arguably one of the most impactful sub-units to have graced the K-Pop scene, Orange Caramel made their debut as a sub-unit in June of 2010 with the single “Magic Girl.” Consisting of three members from Pledis’ first ever girl group AFTER SCHOOL, Raina, Nana, and Lizzy, Orange Caramel saw commercial success as their debut album with the very literal title The First Mini Album peaked at No. 2 on the Gaon charts. In 2014, the trio released what would later be considered as a cultural reset by any K-Pop fan—Catallena. If you are deep into the K-Pop world, you might have seen a clip of three girls exclaiming “Hah!” in turn during the beginning of a performance. The legendary “Catallena” introduction made as much impact online when it went viral as it did when the song entered the charts both domestically and internationally. Orange Caramel’s third single peaked at No. 6 on the Gaon Digital Chart and was included in Billboard’s Top 100 Greatest K-Pop Songs of the 2010s at No. 20. Although no longer active, Orange Caramel left a legacy behind quirky and refreshing concepts in K-Pop with their catchy tunes, eccentric music videos, and memorable stage outfits. Similar to Orange Caramel, Oh My Girl’s first sub-unit OH MY GIRL BANHANA and WJSN’s first sub-unit WJSN CHOCOME kept the quirky concept alive with the releases of “Banana allergy monkey” in 2018 and “Hmph!” in 2020 respectively.

Permanent Sub-Units Within Large Groups

For groups with 10 or more members, they usually operate under a sub-unit system with permanent fixtures within the collective group. In SEVENTEEN’s case, the 13-member group has three permanent sub-units that highlight a specific speciality: hip-hop unit, vocal unit, and performance unit. However, the sub-units’ releases on every album are still under the collective group’s name instead of being specified to their respective unit. SEVENTEEN’s first sub-unit that branched out from the group’s activity was BSS or 부석순 (BooSeokSoon), who officially debuted in March of 2018. The trio, also known by fans as the gag trio in SEVENTEEN with moodmakers Seungkwan, DK, and Hoshi, released their digital single “Just do it” that was first revealed at the group’s fanmeet a month prior to the official release. 

With an “unlimited members” concept, NCT or Neo Culture Technology is the umbrella to many sub-units that exist under it including NCT U, NCT 127, NCT Dream, and WayV. Each unit is in charge of a distinct concept and tackles a different purpose. As a rotational unit, NCT U members change depending on the concept. They debuted in April of 2016 with the double singles “The 7th Sense'' and “Without You.” The debut line up consists of members Taeil, Jaehyun, Taeyong, Mark, Ten, and Doyoung. NCT 127 debuted three months later with “Fire Truck.” The “127” in the sub-unit’s name stands for the longitude coordinate of Seoul, their home city. Following NCT 127 is NCT Dream, a sub-unit that is based on age. They debuted with title track “Chewing Gum” that August. Although the original concept is all members being under 20 that would “graduate” once they hit that age, the team’s structure was reorganized and now has seven members permanently who take part in rotational promotions. NCT’s Chinese unit, known as WayV, focuses on releases in Mandarin. The unit debuted under SM Entertainment’s China-exclusive label Label V with the Chinese version of NCT 127’s “Regular.” Although the “unlimited members” concept might scare those who want to get into the group, NCT’s system helps break down the intimidating member headcount by introducing the members through smaller sub-units.

LOONA is another K-Pop act that used the sub-unit system to help introduce the world to the 12 member girl group. The group’s debut was a project that spanned over two years, featuring individual as well as sub-unit releases. The three sub-units in order of debut are LOONA 1/3 with title tracks “Love&Live” and “Sonatine,” LOONA/ODD EYE CIRCLE with title track “Girl Front” and LOONA/yyxy with “love4eva (feat. Grimes).” The sub-units had music video releases as well as physical album releases which would eventually lead to the debut of the collective group in 2018.

Temporary Sub-Units

In the absence of a group’s members, whether due to military service or unavailability due to the pursuit of other project commitments, situational sub-units are formed. During 2012 when Girls’ Generation would go through a hiatus with the majority of members focusing on individual activities, sub-unit TTS or TaeTiSeo was formed. Consisting of members Taeyeon, Tiffany, and Seohyun, the trio debuted with the EP Twinkle in April of 2012, which became the first album by a Korean artist to rank No.1 on the Billboard World Albums Chart. The title track “Twinkle” also saw domestic success, as it achieved a triple crown on weekly music shows, reigning number one for three weeks in a row. 

In 2017, four out of five members of Pledis Entertainment’s NU’EST joined the boy group survival show Produce 101 Season 2. With Minhyun making the final lineup of the show and becoming a member of the temporary group WANNA ONE, the remaining four members formed NU’EST W. The sub-unit debuted in July of 2017 with “WHERE YOU AT,” earning the group their first win after five years since debut. With the “W” in their name standing for “wait,” NU’EST W carried on promotions as a sub-unit until they disbanded in December of 2018 following Minhyun’s return to the group.

After over a year with no activity and in interim of PRISTIN member Kyla’s hiatus, Pledis Entertainment announced the debut of PRISTIN V. The lineup of five members from the original group released a single album titled Like a V featuring title track “Get It” in May of 2018. As things were looking up for a possible full group comeback, it was announced a year later by the company that PRISTIN had disbanded following the contract termination of seven out of 10 members.

BTOB’s second sub-unit BTOB 4U with members Eunkwang, Changsub, Minhyuk, and Peniel formed in November of 2020 while waiting for Sungjae and Hyunsik to finish their military duties. The sub-unit also participated on Mnet’s competition series Kingdom: Legendary War.

Company Sub-Unit Projects

Oftentimes, labelmates from the same company will partner up for music projects by forming official sub-units. SM Entertainment, YG Entertainment, and CUBE Entertainment are some K-Pop companies that are known to have these cross-group projects. Former 4Minute member HyunA and former BEAST member Hyunseung, both under CUBE, formed the duo Trouble Maker in November of 2011. The sub-unit debuted in December with the single “Trouble Maker” that made waves in the K-Pop scene with their daring and sexy concept. The chemistry-oozing duo proved to be a crowd-pleaser when they snatched the Best Collaboration Performance award at the Mnet Asian Music Awards in 2012. During her time in CUBE before terminating her contract in 2018, HyunA was in sub-unit Triple H with fellow labelmates Hui from PENTAGON and E’Dawn (now known as DAWN). The trio released two EPs with the title tracks “365 Fresh” in 2017 and “Retro Future” in 2018. 

From observation, YG Entertainment’s cross-group sub-units have a trend of being formed in a duo, like HI SIHYUN composed of LEE HI and Akdong Musician’s Lee Suhyun who debuted in 2014 and MOBB composed of WINNER’s MINO and iKON’s Bobby who made their debut in 2016.

Beside forming cross-group sub-units from groups within their company like Younique Unit with members from Girls’ Generation, Super Junior, SHINee, and EXO, SM Entertainment collaborated with Woollim Entertainment to form the cross-company sub-unit Toheart. The duo, consisting of Woohyun from INFINITE and Key from SHINee, debuted with the single “Delicious” that peaked at No. 9 on the Korean charts. 

There are many other sub-units in K-Pop that we weren’t able to touch upon or else this article could be published as a multi-chaptered book, but they are just as iconic as the ones mentioned above. Sub-units like GD&TOP and GD x TAEYANG from BIGBANG, EXO-CBX and EXO-SC from EXO, Red Velvet - IRENE & SEULGI from Red Velvet, JUS2 from GOT7, SISTAR19 from SISTAR, and many more have all played a huge part in diversifying K-Pop. They offer the participating members a chance to experiment with varying sounds and personas, the fans a different side to their idols and the genre with amazing music.