K-pop is all about change, not only in the genre itself but between the members as well. Line-up changes in a K-pop group aren't common, but they do happen, and sometimes it can be so discrete that fans may not even notice the change. This is usually because the line-up changes before the group receive attention. In fact, there may be groups that you actively listen to that you may not have known about the member change! Check out this list of groups that went through a line-up change, whether you knew it or not!
1) Oh My Girl
Debut(April 2015) ~ October 2017: 8 Members (Hyojung, YooA, Mimi, JinE, Seunghee, Binnie, Jiho, Arin)
October 2017 ~ Present: 7 Members (Hyojung, YooA, Mimi, Seunghee, Binnie, Jiho, Arin)
Oh My Girl went through only one member line-up change. JinE stopped promotions for the group in August 2016 due to anorexia and took time off so she could focus on her declining health. While fans were hopeful that she would rejoin for the next album, she did not participate in "Coloring Book" in early 2017. Eventually, she decided to leave the group and the entertainment world due to her health. Some fans do not know of this change because Oh My Girl belatedly saw a surge in popularity after their appearance on Mnet's Kingdom in 2019.
2) A PINK
Debut(April 2011) ~ April 2013: 7 Members (Chorong, Bomi, Eunji, Yukyung, Naeun, Namjoo, Hayoung)
April 2013 ~ Present: 6 Members (Chorong, Bomi, Eunji, Naeun, Namjoo, Hayoung)
A PINK's member line-up change also happened before their breakthrough. The 10-year-old veteran group experienced a line-up change two years after their debut before their "NoNoNo" release. Former member Yukyung left in order to pursue her studies, though there has been controversy regarding the member.
3) Girls Day
Debut(July 2011) ~ September 2011: 5 Members (Jiin, Jisun, Jihae, Minah, Sojin)
September 2011 ~ October 2012: 5 Members (Jihae, Minah, Sojin, Hyeri, Yura)
October 2012 ~ Present: 4 Members (Minah, Sojin, Hyeri, Yura)
Many people do not know about Girls' Day's debut line-up, which included former members Jiin, Jisun & Jihae. The group released their controversial single "Tilt My Head," and that was the first and last album for Jiin & Jisun. The reason for the line-up change isn't clear, but current members Hyeri & Yura have replaced the girls. In October 2012, the group experienced another member change as Jihae left to pursue her studies. Nine years later, we have the four girls that represent Girls Day today.
4) Red Velvet
Debut(August 2014) ~ March 2015: 4 Members (Irene, Joy, Wendy, Seulgi)
March 2015 ~ Present: 5 Members (Irene, Joy, Wendy, Seulgi, Yeri)
The ever-so-popular Red Velvet (who is back with Queendom) did have a line-up change. The lovely ladies went through a member change before their "Ice Cream Cake" comeback in March 2015. Yeri belatedly joined the group, and it was a perfect line-up change as these five ladies represent Red Velvet today.
Debut(February 2016) ~ August 2016: 12 Members (SeolAh, Xuanyi, Bona, Exy, Soobin, Luda, Dawon, Eunseo, Cheng Xiao, Meiqi, Yeoreum, Dayoung)
August 2016 ~ August 2018: 13 Members (SeolAh, Xuanyi, Bona, Exy, Soobin, Luda, Dawon, Eunseo, Cheng Xiao, Meiqi, Yeoreum, Dayoung, Yeonjung)
September 2018 ~ Present: 10 Members (SeolAh, Bona, Exy, Soobin, Luda, Dawon, Eunseo, Yeoreum, Dayoung, Yeonjung)
The lovely ladies of WJSN went through quite a few line-up changes, though the most recent one is not official. Strong main vocalist Yeonjung was added to the group after her participation in Produce 101, and she completed the vocal line for the group. In 2018, the Chinese members have not been participating in group activities, and though the members haven't officially left the group, they have not been active for over three years, and it does not look like they will be returning soon as they are focusing on individual activities in China.
Debut(February 2012) ~ August 2012: 6 Members (Dami, Yuji, Haeryung, LE, Hani, Junghwa)
August 2012 ~ Present: 5 Members (LE, Hani, Junghwa, Solji, Hyerin)
The pioneers of "reverse run" popularity EXID also saw member changes before they exploded with "Up & Down." When the three original members Dami, Yuji, and Haeryung left due to company problems (and later re-debuted as BESTIE), two power vocalists Solji & Hyerin, joined the group. Note that it still took two long years before these ladies received any sort of recognition in the K-pop world.
7) Hello Venus
Debut(May 2012) ~ July 2014: 6 Members (Yooyoung, Nara, Alice, Yoonjo, Yoo Ara, Lime)
July 2014 ~ Disbandment(May 2019): 6 Members (Nara, Yeorum, Alice, Yooyoung, Seoyoung, Lime)
Hello Venus initially debuted as a collaboration with PLEDIS & Fantagio. Once the collaboration ended in July 2014, Fantagio took full force and added two new members to the line-up it is today. Though the girls are not active anymore, Hello Venus did release some great hits that are widely loved today!
Well, there you have it! These were some of the many K-pop girl groups that experienced a rather more discrete line-up change. Part of this is because these line-up changes happened before the group's official breakthrough -- was there a group that you did not know about? Was there another group that experienced an even more discrete line-up change? Let us know in the comments below!