The group originally debuted with four members: Jun Hyo-seong, Jung Ha-na, Song Ji-eun and Han Sun-hwa.

Secret's debut single did not meet great success and it was not until the following year that the group saw a rise in popularity.

In 2011, Secret adopted a girl-next-door image through songs like Shy Boy and Starlight Moonlight which led the group to major success.

With the group's success in South Korea throughout 2011, Secret sold over seven million in digital download sales.

After almost a year of absence from the South Korean music industry Secret released their third extended play "Poison" in September 2012 followed by the digital single Talk That in December.

[14] On August 3, 2011, the group released their first single in Japan, "Madonna", which debuted at number nine on the Oricon charts.

They have attended the KBEE (Korea Brand & Entertainment Expo) in Paris, France, on December 1 to 3, 2011.

"Talk That" received generally positive reviews from critics, most of whom had praised the song for its mature musical style and concept as opposed to their previous singles.

Hyoseong, Jieun and Sunhwa received only a few scratches and knee pain, but Hana suffered broken ribs and a bruised lung and therefore halted from Secret's activities in order to recover.

[34][35] On December 27, Sunhwa and labelmate B.A.P's Youngjae teamed up to release a digital single titled "Everything is Pretty" as a present for Secret and B.A.P fans.

[38] On March 29, Secret held their solo concert in Singapore,[39] performing in front of 5,000 fans at the Marina Bay Sands Convention Hall.

[40] YooHoo managed to top real time charts such as Mnet, Bugs Olleh, and Sorribada.

[46] On September 26, 2016, it was announced that Sunhwa would be leaving the group after deciding not to renew her contract with TS Entertainment in order to pursue a career in acting.

[50] On March 5, Hyoseong's lawyer revealed that she had filed a civil lawsuit against TS Entertainment in September 2017 to confirm that her contract with the agency is no longer valid.

TS Entertainment also transferred the management rights conferred by its exclusive contract with the singer to another party without the consent of Jun Hyoseong herself.

[51] Retro is the main musical style of the majority of Secret's singles, although the group has channeled other genres such as pop, dance, R&B, and hip-hop.

[52] Secret were originally formed with an intention to be an RnB and Hip-Hop group as seen in their debut single, "I Want You Back".

As Seoulbeats wrote, "Originally debuting with an urban RnB concept, the girls of Secret have transformed themselves into the queens of retro ever since their breakthrough hits with “Magic” and “Madonna”.

Furthermore, with Wonder Girls recently vacating their long-held affair with retro in favor of a more fresh and futuristic(?)

[55] Secret's output, particularly with their work with Kang Ji-won and Kim Ki-bum, makes use of live instruments such as brass, saxophones and drums with the incorporation of synthesizers and electric guitars.

[52][53] While reviewing "Poison", Seoulbeats commented that "the composition [of "Poison"] contains a very fitting saxophone hook along with recognizable brass and drum instrumentals that have become the trademark of Secret and their in-house composers, Kang Ji-won and Kim Ki-bum, who have produced all of Secret's retro hits.

"[52] Seoulbeats concludes that "Secret has carved out its conceptual niche in the K-pop market by developing a distinct and consistent style, and thus they are now in a position to elevate their success and recognition in the industry.

[52] Seoulbeats wrote, "Secret embarked on an aegyo phase in their following release of “Shy Boy" although with much voiced displeasure from the members.

Despite the radical change in their personalities, their style remained consistent in staying with and expanding upon their retro identity.

Secret kept its cute imagery with their following single "Starlight Moonlight" until the release of "Love is Move" and "Poison".

[52] During their promotions with "Poison", Jun Hyoseong commented "Secret has always been known as a cute group that appeals to the general public.

"[57] The group's popularity and success in Korea has led to endorsement deals such as Gueoseu Chicken, Googims mall, Grand Mer(Online Fishing Game),[60][61] Nike,[62][63] Nene Chicken,[64][65] Good Day Soju[66] and Parkga[67] among others.

[73] In 2010, Secret released their hit single "Magic" which was nominated at the 12th Mnet Asian Music Awards for Best Dance Performance by a Female Group.

The song was their first Triple Crown in KBS's Music Bank and garnered them multiple awards and nominations.