I.O.I reunite 10 years on: 9 members return, new single '갑자기' hits No. 1

'너무너무너무' turned 10 — and so did the reunion promise

Ten years ago today, I.O.I dropped their second mini album Miss Me? and swept No. 1 on 8 music charts with the double title track 너무너무너무, written and composed by Park Jin Young. The track held the top spot on Melon's combined weekly chart for the week of October 17–23, 2016.

The album launched at YES24 Live Hall in Gwangjang-dong, Gwangjin-gu, Seoul. The full tracklist: 너무너무너무, 잠깐만, 내 말대로 해줘, PING PONG, and 음 어쩌면.

I.O.I was an 11-member girl group formed through Mnet's survival program Produce 101. They were active only from May 2016 to January 2017. At disbandment, members were already talking reunion. Jung Chae-yeon said the group "promised to not think of the remaining time as the last, but to enjoy and work hard." Yoo Yeon-jung and Choi So-mi both publicly committed to a 5-year reunion. So-mi added, "By then I will be 21 years old."

The 5-year promise became a 10-year wait

The 5-year mark came and went. In May 2026, a decade after their debut, the reunion finally happened. Not with all 11 members. Ju Gyul-kyung and Kang Mi-na did not participate. The nine who returned: Im Na-young, Chungha, Kim Se-jung, Jung Chae-yeon, Kim So-hye, Yoo Yeon-jung, Choi Yoo-jung, Kim Do-yeon, and Choi So-mi.

The 9-member unit released a new single, 갑자기, which topped Melon and other major music charts. Ten years, two members short, still No. 1.