Kim Hye-jun Trained Alongside Elementary Schoolers to Become A Shop for Killers Season 2’s Action Star

Four months before A Shop for Killers began filming its first season, Kim Hye-jun was folding herself into a Muay Thai gym alongside a class of elementary schoolers. She was in her late twenties at the time, one of the oldest bodies on the mat, working through the same drills as a room of ten-year-olds because there was no track built for an actor easing gently into a physical role. Two years and one Disney+ hit later, she’s aiming an assault rifle down a corridor in the show’s final episodes, and the martial arts director who trained her says he barely recognizes who she used to be.

That director is Jeon Jae-hyung, known in the industry for his stunt work on the Crime City film franchise — a name that carries real weight in Korean action cinema. In A Shop for Killers Season 2, which wrapped its eight-episode run on Disney+ on August 12, Kim plays Jung Ji-an, who inherits the secret weapons shop Murthehelp from her uncle, Jung Jin-man (Lee Dong-wook), after losing almost everyone she loves. The season pits her against Babylon, the assassin organization her uncle once led, now expanding into East Asia with a fresh set of operatives closing in on Ji-an.

For this season, Jeon’s team narrowed the training almost entirely to guns. “We placed a lot of emphasis on firearm handling, posture, footwork, and shooting techniques,” he said, describing weeks spent drilling stances and reloads until they stopped looking performed. Kim described the shift in blunter terms of her own: “I will show more diverse gun action than before. I practiced tactics and stances extensively.”

The result shows up in how she talks about her own character now. “In Season 1, you saw Ji-an as more of a girl, but in Season 2, you will see her instincts as a killer emerging more strongly,” Kim said. It’s not a small claim — Ji-an spends the first season being protected, and by the second she’s the one other people are afraid to cross.

Jeon put it more bluntly still: “She feels like a completely different person compared to when we first met. Now, she is a fully accomplished action actress.” That’s not a small thing to hear from him specifically. The Crime City series he works on is Korea’s most consistently successful homegrown action franchise, several entries deep and each one a certified box-office hit — the kind of production where sloppy gunwork gets noticed immediately, by audiences who’ve been trained by the franchise itself to expect the real thing.

It’s a strange sentence to read next to Kim’s actual resume, though. She debuted in 2015 in the queer romance web series Lily Fever while still studying theater and film at Hanyang University, spent a season on Saturday Night Live Korea, and then broke through in an entirely different register: playing the doomed, grieving Queen Consort Cho in Kingdom, one of Netflix’s first major Korean originals.

The awards that followed weren’t for action, either. Kim won Best New Actress at the 2019 Blue Dragon Film Awards for the quiet domestic drama Another Child, then took Best New Actress – Television at the 2022 Baeksang Arts Awards for Inspector Koo, where she played a cold-case obsessive nicknamed “K” opposite Lee Young-ae. Genre work wasn’t new to her by that point — precision under pressure already was. What A Shop for Killers asked for was something closer to athletic literacy: the ability to hold a rifle like an extension of her arm instead of a prop she’s handling for the first time on set.

Critics reviewing the finale have picked up on that exact distinction. One review from Cineplay credited her with a “layered portrayal” that kept Ji-an’s emotional throughline intact even as the show accelerated into its action set pieces, crediting the “repeated hand-to-hand combat and firearms training” visible in her posture and timing — not just her wardrobe or the choreography around her. The same review noted something else worth sitting with: under enough pressure, Ji-an starts to resemble the uncle she spent Season 1 trying not to become, which is arguably the more difficult performance note to hit — action training gets a character to hold a rifle correctly, it doesn’t automatically get her to carry someone else’s damage convincingly.

2026 also happens to mark ten years since Kim’s professional debut, and Korean entertainment press has framed the year as something of a victory lap: an action franchise on one end, the romantic comedy My Bias, My Boss on the other. A Shop for Killers itself had already earned her a Best New Actress nomination at the 2024 Blue Dragon Series Awards, back when Season 1 was still the smaller, newer story.

None of it erases the image of a twenty-nine-year-old squeezed onto a Muay Thai mat next to a room of fifth-graders. If anything, that’s the detail that makes the rifle scenes land — the distance between where the training actually started and where the camera eventually caught up to her.