The highly anticipated Korean romance film 'Once We Were Us' has faced criticism as the official trailer was put out, with fans expressing frustration on social media over what many are calling another "baffling" casting decision featuring an age gap.

According to Koreaboo, the film stars 29-year-old Moon Ga Young and 42-year-old Koo Kyo Hwan as ex-lovers Jung Won and Lee Eun Ho, respectively—characters that are written to be the same age. The contrast between the real-life ages has raised concerns among moviegoers, many of whom felt that the casting choice undermines the believability of the story.

The trailer from Showbox shows the couple in a series of emotional flashbacks and modern-day meetings. But the sneak peek did little to mollify critics. One viewer's reaction: "This really pisses me off."

Another viewer questioned the production decisions: "Koo Kyo Hwan does look young for his age group... But that does not mean he can play a young character. Who's the casting director???"

With the release of screenshots along with the trailer, debate raged on theqoo; several said the age gap was apparent and irritating. Comments only introduced neutrally included, "If you want the characters to be around the same age, cast actors who are around the same age. Please."

Others were concerned with the faithfulness of the film to its source material. The Korean remake is based on 2018 Chinese romance "Us and Them," highly loved in the country. A viewer shared disappointment and said, "Wow... I would not have known this is a remake of Us And Them. They're f*cking over the original..."

Though Koo Kyo Hwan has received praise in the past for his versatility and his unique screen presence, the age-gap debate remains an issue deeply seated in the Korean entertainment industry. Critics argue that the pattern continues to repeat, as we see very often with a significantly older man cast alongside a younger woman, therefore demonstrating a lack of authenticity in the presentation of romantic narratives.

Some commenters even suggested that this could potentially affect the chemistry between the leads: "Not only do these two look decades apart, but also they have zero chemistry."

Once "We Were Us" is set to be released on December 31, 2025 (KST). It is about two former lovers who coincidentally meet on a plane bound for Korea, compelling them to confront unresolved emotions and the relationship they left behind.

Though discussions continue to swirl in online threads, no one is quite sure the review will be any different, as the film continues its journey to reigniting the box office once more.