In addition to her musical career, the singer also appeared in several native programs and series, most notably We Got Married and All My Love, where she co-starred alongside 2AM's Jo Kwon.

Son Ga-In was noticed by the existing members of Brown Eyed Girls after she was eliminated during auditions for the popular South Korean reality series, Let's Coke Play!

She was approached by composer Ahn Jung-hoon and invited to audition at Brown Eyed Girls' company, Nega Network, eventually joining the group.

[3] In the same year, she performed a duet "Must Have Love" with SG Wannabe's leader Kim Yong-jun, which became her first number one hit during the Christmas season.

She also released a digital single, titled "We Fell in Love" (우리 사랑하게 됐어요) with then We Got Married partner 2AM Jo Kwon, composed by fellow member JeA, Kim Eana, and produced by Lee Min-soo.

After the promotions of Brown Eyed Girls' fourth album, it was revealed that Gain had signed a contract with LOEN Entertainment to manage her solo career.

On April 13, 2013, she was featured in PSY's music video "Gentleman", along with the "arrogant" dance which was popularized in the Brown Eyed Girls song "Abracadabra".

Considered as a "bolder" move for herself, the album was preceded by "Fxxk U", which received mixed reactions from the public due to its theme dealing with domestic violence; however, it was praised by critics.

It was announced that Gain would go on to release her fourth solo mini-album (fifth overall), titled Hawwah in February 2015 as a follow-up to her previous Truth or Dare EP.

During an interview with Billboard, Gain announced that her home group would return with a new album to coincide with their tenth anniversary since debuting in 2006 and the possibilities of another solo release in 2015 also.

In July 2021, Gain apologized for illegally using propofol, an anesthetic drug prohibited from being used for purposes other than surgical treatments in South Korea.

In an apology issued by Mystic Story, the parent company of Apop, it was stated that Gain "made a reckless choice due to severe depression and a sleep disorder.