Let's talk about that 2016 fever dream for a second. If you were anywhere near the K-drama scene back then, you remember the absolute chaos. It wasn't just a show; it was a weekly battleground. And at the center of that storm? Seo Kang Joon.
Specifically, his role as Baek In Ho in Cheese in the Trap.
Even now, years later, you can’t mention this drama without starting a debate. It’s kinda fascinating. On one side, you have people who would literally die for Baek In Ho’s dimples. On the other, you have purists who feel the drama did Park Hae Jin (who played the lead, Yoo Jung) incredibly dirty. Honestly, both things can be true at once.
The Breakout: How Seo Kang Joon Stole the Show
Before 2016, Seo Kang Joon was that "pretty rookie" from the actor-group 5urprise. He was doing okay, but Seo Kang Joon Cheese in the Trap changed everything. He wasn't just a supporting actor anymore; he became a phenomenon.
He played Baek In Ho, a disgraced piano prodigy with a temper as hot as his visuals. He was loud. He was messy. He wore those oversized flannels and had that "dog fur" nickname for Hong Seol (Kim Go Eun). He was the literal definition of a tsundere—the guy who acts like a jerk but will secretly leave a bag of self-defense items on your doorstep because he's worried about your stalker.
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The chemistry between Seo Kang Joon and Kim Go Eun was... well, it was dangerous. It was so natural that people started jumping ship from the main couple. That’s where the "Second Lead Syndrome" went from a trope to a full-blown controversy.
The Screentime Scandal Nobody Talks About Enough
If you weren't there for the live airings, you missed the drama behind the drama.
Halfway through the series, things got weird. The male lead, Yoo Jung, started disappearing. Seriously. There were episodes where the supposed "Main Character" barely had ten minutes of screentime. Meanwhile, the plot started revolving heavily around Baek In Ho’s piano journey and his blossoming friendship with Seol.
- The Webtoon Author’s Outrage: Soonkki, the creator of the original webtoon, actually went public with her frustration. She claimed the production team stopped consulting her after episode six.
- Park Hae Jin’s Deleted Scenes: It came out later that scenes Park Hae Jin had already filmed—important character development stuff—were cut.
- The Reshoots: Rumors swirled that the PD (director) was so enamored with Seo Kang Joon’s performance that they kept adding more for him to do.
It put Seo Kang Joon in a tough spot. He was doing an incredible job, but he was becoming the face of a production nightmare. Fans of the webtoon were livid because the "mystery" of Yoo Jung's character was being replaced by a standard love triangle.
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Why Baek In Ho Was Actually the Better Character (For Some)
Let’s be real for a minute. Yoo Jung was... a lot. He was manipulative, borderline sociopathic, and honestly kind of terrifying at times.
Baek In Ho was the opposite. He was transparent. If he was mad, he yelled. If he liked you, he teased you until his face turned red. For many viewers, he felt like the "healthier" choice, even if he was a bit of a disaster.
Seo Kang Joon brought a vulnerability to the role that wasn't necessarily on the page. You could see the heartbreak every time he looked at his scarred hand—the hand that ended his piano career. He played the "pitiful" angle so well that you couldn't help but root for him to get something good in his life, even if it wasn't the girl.
Life After the Trap: The Seo Kang Joon Evolution
After the dust settled on the Cheese in the Trap finale (which, let’s agree, was a total mess), Seo Kang Joon didn't slow down. He used that momentum to prove he wasn't just a "second lead" guy.
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He took on massive challenges. He played a human and a robot in Are You Human Too?, which is still one of the most underrated dual performances in K-drama history. Then he went dark and gritty in Watcher. He proved he had the range to move past the "lovable rebel" archetype.
His most recent work, including the 2025 hit Undercover High School, shows a much more mature actor. But for a huge chunk of the international fanbase, he will always be the guy playing the piano in a dusty practice room, arguing with "Dog Fur."
What You Should Do Next
If you’ve never seen the drama but want to understand the hype around Seo Kang Joon Cheese in the Trap, here is how to approach it without losing your mind:
- Watch the first 10 episodes: This is when the show is at its peak. The atmosphere is moody, the college life feels real, and the tension is perfect.
- Read the Webtoon: If you find yourself confused by Yoo Jung's behavior or why everyone is so mad about the ending, the webtoon is the only place you'll get the "real" story.
- Appreciate the Performance: Regardless of the production drama, watch Seo Kang Joon's eyes. The way he shifts from comedy to absolute grief is a masterclass in acting.
Whether you're Team Jung or Team In Ho, there's no denying that Seo Kang Joon's portrayal remains one of the most impactful "second leads" in the history of the medium. He didn't just play a character; he hijacked a whole production just by being too good to ignore.