[9][10] Promotion began on February 25, 2013, with the release of Rise's teaser video, followed by Sojung's on the 26th, EunB's on the 27th, for Zuny's on the 28th, and March 1 for leader Ashley respectively.

[13] The group's debut mini-album Code#01 along with the title song "Bad Girl" and accompanying music video was released on March 7, 2013.

The group's return was originally set for July 25, 2013, however member Zuny had an unexpected leg injury which pushed back their comeback until August.

"[22] A still-cut of the first music video teaser was released on February 6, 2014, showing member Kwon Rise lying in transparent plastic wrap.

[25] A second video teaser featuring all of the members recreating kiss scenes such as the fairy tale "The Frog Prince" was released on August 5, 2014.

On September 3, 2014, at around 1:30 am (KST), the group was involved in a serious car collision while returning to Seoul after attending the recording of KBS "Open Concert" at DGIST.

[34][35] EunB was declared dead on arrival by the time the paramedics reached Sungbin Medical Center, while the remaining six passengers were rushed to various hospitals.

[36][37] Sojung and Rise, who suffered the most serious injuries, were taken to the Catholic University of Korea St. Vincent's Hospital in Suwon, listed under critical condition.

Rise's condition quickly deteriorated and she was moved to Ajou University Hospital, where she eventually died four days later on September 7, 2014, at 10:10 am (KST).

[32] On September 15, 2014, Polaris Entertainment released a tribute music video of "I'm Fine Thank You", using behind-the-scenes footage of the group to honor EunB and Rise.

[51] On November 12, 2014, Park was arrested and indicted on the charge of causing a fatal collision under the Act on Special Cases Concerning the Settlement of Traffic Accidents and was sentenced to a year and two months in jail on January 15, 2015.

[57] On April 26, 2015, it was reported that Zuny, Ashley, and Sojung had resumed their practice schedule while continuing to receive counseling and follow-up treatments for injuries sustained from the crash.

The concert featured Polaris artists, including Kim Bum-soo and Rumble Fish, and a performance of "I'll Smile Even If It Hurts" by Ashley, Sojung, and Zuny.

[60][61] On September 3, 2015, Sojung and Polaris artists Kim Bum-soo, IVY, Han Hee-jun, Rumble Fish, and Sun Woo released a cover of "I'm Fine, Thank You" in memory of EunB and Rise.

Polaris Entertainment noted the end of February as a tentative comeback date and clarified that there were no future plans to recruit new members.

Billboard magazine noted that the group blends in "modern electro-pop" with "classic throwback elements" and powerful vocals.

[78][79][80] Their follow-up single, "Hate You" was marked as a departure, returning with a mid-tempo dance song with a combination of brass and acoustic guitar arrangements.

[82] In an interview with enews on their digital single "So Wonderful", member Ashley explained the song was a continuation of their previous releases but added that they had incorporated the use of more instruments and were going for a "retro feeling from the 80's.

"[83] Their first release after the crash, Myst3ry, shifted into an R&B sound with the lead single "Galaxy" described as a "mid-tempo song that invokes a gloomy and dreamlike mood".