Following the success of her third solo release "Gashina", which articulated a cynical attitude in the aftermath of a breakup, Sunmi conceptualized "Heroine" as a prequel narrative to it.

She drew inspiration from the Adrian Lyne film 9½ Weeks (1986), expressing a "show must go on" sentiment as the protagonist deals with a turbulent relationship.

On December 18, 2017, it was revealed that the singer was preparing for a comeback with the goal to release a new song in January 2018 with no further details.

[12] There are concerns that the song has plagiarized Cheryl's debut solo single "Fight for This Love", which was released in 2009.

[13] It later concluded with stating, "We unequivocally reveal that ‘Heroine’ is 100 percent an original creative work with absolutely no reference to the song that has been named in the controversy.