Yeon Sang-ho brings the zombies back in 'Colony'

Yeon Sang-ho is done playing small.

The "Train to Busan" (2016) director's last film, ultralow-budget thriller "The Ugly," was a bare-bones social drama shot in three weeks with a skeleton crew. Before that was Netflix's "Revelations," a psychological slow burn that shed the more fantastical elements the director had built his name on.

Now, with "Colony," the director behind Korea's biggest zombie export is back to what made him famous: zombies.

"This is a film where everything I found exciting about 'Train to Busan' and 'Peninsula' finally gets the room to breathe," Yeon said at Monday's press conference at CGV Yongsan in Seoul, referring also to the film's 2020 sequel. "But the infected here are completely new, different from anything I've shown before."

"Colony" traps survivors inside a sealed building during an outbreak of a fast-mutating virus triggered by a biotech conference gone awry. Yeon framed the premise in terms of a fear he has been chewing on for a while.

"Zombie stories are great at showing the anxieties a society won't say out loud," he said. "What scared me this time was the speed at which information spreads, how the crowd starts thinking as one and the individual just falls apart."

Half the buzz, though, is about the cast. Jun Ji-hyun, known internationally as Gianna Jun, returns to the big screen for the first time since period blockbuster "Assassination" in 2015. The anticipation is hard to miss for an actor who, at 45, still ranks among the most bankable female leads in the country.

"It feels exciting to be back in a theater with a movie," Jun said. "I've been a genuine fan of the director's work for a long time, so getting to be part of his world was a no-brainer."

Yeon, for his part, seemed starstruck by his own lead. He recalled their first meeting at a cafe: "The moment she walked in, it felt like a movie had started playing. She was just sitting there, and I thought, that's a movie star right there."

The director praised Jun's range, pointing to her work across genres from "My Sassy Girl" (2001) to "Assassination." "She managed to compress that entire spectrum into a single performance here. There's a reason she's a superstar."

Art house favorite Koo Kyo-hwan plays the rogue biologist behind the outbreak. This marks the actor's fourth collaboration with Yeon, following "Peninsula," horror series "Parasyte: The Grey" and miniseries "Monstrous."

"It felt like shooting an omnibus film, meeting all these different characters at once," Koo said. "Each one's story was so compelling, I kept thinking they could spin off into their own thing."

Ji Chang-wook rounds out the main cast as a security guard who spends much of the film carrying his paraplegic sister, played by Kim Shin-rok, on his back. Shin Hyun-bin, last seen playing a female lead whose face never appears on screen in "The Ugly," plays a survivor weighing impossible choices.

Despite the genre trappings, Yeon insists the film is a family-friendly watch. "It's rated 15-plus, same as 'Train to Busan,' but I know plenty of elementary schoolers saw that one," he said.

"I showed some bits from 'Colony' to my fifth-grade daughter on my phone as a test run. She had a good time."

"Colony" opens in theaters in May.