Come on, you know that feeling — that crazy pang of dissatisfaction you felt as soon as 30 seconds of screen time from the second couple turned the lead couple into bits of set decor in your K-drama.

Take a look at eight second-lead couples who had chemistry on such high levels that they each left an impression in every scene.

Gu Seung Jun and Seo dan

Let's start with a fan favorite: Crash Landing on You Gu Seung Jun and Seo dan. Even the viewers who didn't enjoy the drama have admitted that this couple was the only reason they kept watching the series.

While Crash Landing on You has got more of its attention focused on the fairytale-esque relationship between Ri Jeong Hyeok and Yoon Se Ri, played by Hyun Bin and Son Ye Jin, respectively, the second-lead couple, portrayed by Kim Jung Hyun and Seo Ji Hye, began melting hearts, differently.

Together, they gave the drama another vibe of all the banter, reluctant attraction, and heart that had fans on their side just as much as the lead couple.

Their courtship had an inauspicious start, as the playful Seung Jun's roguery didn't mesh well with the frozen poise of Seo Dan.

However, we get to see the softer side of Seo Dan when she starts to warm up around Seung Jun, becoming more human and losing the cold or stoic vibe we read from her character throughout the drama.

The incredible chemistry between Jung Hyun and Ji Hye made each scene electrifying. The bittersweet ending to their ill-fated love left fans to mourn the fact that they never made it work and to wonder "what if."

So Yi-Jung and Ga-Eul

Anyway, it would be a sin not to talk about Boys Over Flowers' So Yi-Jung and Ga-Eul. Though the drama's primary couple faced many dramatic obstacles, it was Yi-Jung and Ga-eul's tender yet fraught romance that won viewers over—and gave many their first serious case of second-lead syndrome.

Their chemistry was effortless and real, and fans have been rooting for them from the beginning. We witnessed her supporting him and Yi-Jung returning her love.

It was inspiring to know that it takes time to let the pain go before one can truly love again. That was why it was heartbreaking for us to watch even more.

Kim Bum and Kim So-Eun's on-screen chemistry was so palpable that fans were obsessed with their potential pairing in real life, even shipping them together.

The hype was only enhanced because the two were very close to recording the drama. Today, they are the originators of the idea of a second-lead syndrome couple.

Sun Deok-sun and Kim Jung-hwan

Sun Deok-sun and Kim Jung-hwan of Reply 1988 also belong to the classic second-lead couple pair.

Anyone who has ever watched the Reply series knows how much the show loves to play with viewers' hearts. Reply 1988 took things a step further with the iconic love triangle, or rather love hexagon, between Deok-sun, Jung-hwan, and Taek.

You could see the chemistry between Deok-sun and Jung-hwan literally from episode one. He was so quiet about his love that he made fans root for him — waiting for her every morning, buying her pink gloves acting like Secret Santa behind her back, and protecting her on the bus.

We swooned and ached with every passing episode as Jung-hwan encompassed the second-lead syndrome like no other. But like traditional Replied fashion, the show turned things on their ears, giving Deok-sun to Taek in its place.

Needless to say, that was a plot twist fans did not see coming, as it drove a nearly in-fathomable wedge between fandom.

Even though Taek was adorable, Jung-hwan was the winning soulmate in the eyes of many of us who loved him quietly but thoroughly.

His silent emotions and struggle to confess made him heartbroken all the harder – thus rendering him one of the most iconic second leads in K-drama history.

But that was not all as there was more to the hype than that. Then, in real life, Ryu Jun-yeol and Hyeri broke hearts when they confirmed their dating status, causing a media frenzy.

Their on-screen chemistry was even more special because their real-life relationship lasted for seven years.

Young-seo and Cha Sung-hoon

On this list, we cannot miss Jin Young-seo and Cha Sung-hoon, the second-lead couple of A Business Proposal.

Their romance was a whirlwind of crazy chemistry and playful talk, played by Seol In-ah and Kim Min-kyu, who warmed the hearts of fans across the globe.

The ill-fated run-in at a convenience store to their first kiss brought fireworks.

Grim Reaper and Sunny

Coming in next is the relationship between the Grim Reaper and Sunny in Goblin.

Although the central plot revolves around the Goblin and his wife, Yoo In-na and Lee Dong-wook outshine them with their tragic yet so beautiful romance.

The chemistry between them was palpable. Every scene was tense with desire and indelibly classic.

Yoon Myeong-joo and Seo Dae-young

Finally, we have the second couple in Descendants of the Sun. As obsessed as everyone was with the leads, Song Joong-ki and Song Hye-kyo, many were convinced that Yoon Myeong-joo and Seo Dae-young were the real couple goals.

Together, these two gave the audience one of the most intense cases of second-lead syndrome with a bang. The slow burn, tension, and heartache that came along with their love story often completely overshadowed the main couple.

Myeong-joo, the bravest and most biased army doctor, who, despite Dae-young constantly trying to push her away, was not ready to give up on loving him because she believed Dae-young was not enough of a man for her.

Their chemistry was undeniable in every stolen glance and quiet moment of vulnerability. Fans were cheering for Myeong-joo with her fire and Dae-young with his soft, quiet love.

Kim Ji-won and Jin Goo acted well enough to earn every viewer's heart, which is now totally glued to the screen.

These second-lead duos not only stole the show, but they also became some of television's most memorable pairings, the kind that remind us that it's the second love story we will never forget.