AceShowbiz - Sofia Carson and KJ Apa were given the freedom to create the back stories for their characters love story by "Songbird" director Adam Mason.

The movie follows Apa's character, a bicycle messenger, trying to save his girlfriend from life in a government pandemic camp in a world where COVID-19 has mutated to deadly COVID-23.

And in an interview with Buzzfeed, Sofia opened up about how she and co-star KJ Apa were able to write Nico and Sara’s love story together.

"One of my favorite things that I got to do in the role - and that's thanks to our director, Adam Mason - (was that) he wanted us - KJ and I - to have a voice in Nico and Sara," Sofia explained. "So, he didn't tell us who Sara and Nico were (before the events of the film) - he wanted us to write their story."

She adds that "before we started shooting, I sat down that weekend and I wrote Sara's story from start to finish. Where she was born, who her mother was, her relationship with her mom, what her fears are, how she met Nico - everything that made Sara who she is in order to bring her to life."

"We got together that weekend, that Saturday, and we spent the whole day bringing our love story to life: the first moment Sara and Nico met, the thing about Sara that made Nico fall for her - someone he's never seen, only someone he's heard through the door," she continued.

On Friday, December 11, Carson stunned on the red carpet in a gorgeous pearl gown by Prada at the private screening of "Songbird" in Beverly Hills, California.

Demi Moore, Craig Robinson, Bradley Whitford, Peter Stormare and Alexandra Daddario also star in the film, which is produced by blockbuster king Michael Bay.

"Songbird" is out on demand now.