On June 24, 2015, JYP Entertainment announced that the Wonder Girls would be making a comeback after a three-year hiatus.
A representative of the agency confirmed that former member Sunmi would re-join the group for the first time since withdrawing in 2010.
Rather than a dance group, the Wonder Girls returned as a four-member band with each member playing an instrument: Yubin (drums), Yeeun (keyboard), Hyerim (guitar), and Sunmi (bass).
Their comeback featured a retro, 1980s sound resonant throughout the album, similar to some of their past releases.
On August 2, "I Feel You", the lead single from album, was released.
The group released the album, titled Reboot on August 3.
The album was a commercial success, charting number five on Gaon Albums Chart and number two on Billboard World Albums.
Each member participated in the composition and production of the album.

On October 2, it was announced that the Wonder Girls would host an episode of Saturday Night Live Korea.
They performed their hits "I Feel You", "Nobody", and "Tell Me".
On December 27, they performed at SBS Gayo Daejeon, and on December 31 at 2015 MBC Gayo Daejejeon.
Reboot was ranked No.
1 on The 10 Best K-Pop Albums of 2015 by Billboard, and also No.
18 on The 20 Best Albums of 2015 by FuseTV.
On June 24, 2015, JYP Entertainment announced that the Wonder Girls would be making a comeback after a three-year hiatus. A representative of the agency confirmed that former member Sunmi would re-join the group for the first time since withdrawing in 2010. Rather than a dance group, the Wonder Girls returned as a four-member band with each member playing an instrument: Yubin (drums), Yeeun (keyboard), Hyerim (guitar), and Sunmi (bass). Their comeback featured a retro, 1980s sound resonant throughout the album, similar to some of their past releases. On August 2, "I Feel You", the lead single from album, was released. The group released the album, titled Reboot on August 3. The album was a commercial success, charting number five on Gaon Albums Chart and number two on Billboard World Albums. Each member participated in the composition and production of the album.
On October 2, it was announced that the Wonder Girls would host an episode of Saturday Night Live Korea. They performed their hits "I Feel You", "Nobody", and "Tell Me". On December 27, they performed at SBS Gayo Daejeon, and on December 31 at 2015 MBC Gayo Daejejeon. Reboot was ranked No. 1 on The 10 Best K-Pop Albums of 2015 by Billboard, and also No. 18 on The 20 Best Albums of 2015 by FuseTV.
Wonder Girls