"Gashina" is Sunmi's first release since the disbandment of Wonder Girls and the expiration of her contract with JYP Entertainment.

It was released as the lead single from her second Korean-language EP Warning.

Written by Teddy Park, Sunmi, Joe Rhee, and 24, the song was described as a "dancehall-style synth-pop number that rocks an Eastern-style atmosphere and a distinct rhythmic bass sound".

[2] The physical copy of "Gashina", titled Sunmi Special Edition Gashina, entered at number 16 on the Gaon Album Chart, on the chart issue dated August 20–26, 2017.

[3] The physical CD sold 2,954 copies and placed at number 56 for the month of August.