BERLIN: "PAST LIVES" opens with a shot of the three main characters at a bar in New York as two other patrons guess how the trio know each other, setting up a love story drawing on the Korean concept of "inyeon," or how people end up in each other's lives.

That scene re-creates a moment from director Celine Song's life that inspired her to make the film, her first feature, which premiered at the Sundance Film Festival to rave reviews.

The Korean-Canadian director recounts visiting a bar with her American husband and a childhood sweetheart from Korea.

"I was looking around the bar and seeing the way that people were looking at us. And I was like 'oh, they're all just wondering who we are to each other and they have no idea'," Song told Reuters at the Berlin Film Festival on Monday.

"I was like, well, what if I really decided to tell you who we are to each other?" said Song.

In the film, Nora, played by Greta Lee, must navigate the inyeon between her, her childhood sweetheart from pre-emigration days in South Korea - Hae Sung (Teo Yoo) - and her life in New York City with her husband Arthur (John Magaro).

As Nora explains to Arthur before their first kiss, inyeon is the idea that when two people brush against each other in a crowd, that's the culmination of events that have taken place over thousands of years.

"We like to say that we actually have union together. This idea from the movie that we've all known each other from our past lives," Lee told Reuters.

"I really hope that people come for the romance and for the love and the idea of just a simple story about love," she said. "But maybe they can leave with something bigger about life and about what connects us to each other as human beings."