Actors Kim So Eun and On Joo Wan sat down with SBS Plus's 'Stargram' on this week's broadcast. �

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On the day of filming, it was Kim So Eun's birthday, so On Joo Wan came to the set with a surprise cake! The MCs asked how they know each other, and Kim So Eun revealed, "He's dating my best friend [Jo Bo Ah]. The three of us see one another often. It's been over ten years since I met On Joo Wan. I first met him when I was in middle school, I think."

The MCs said, "What's the age difference between you two?" and she joked, "It's big. At the time, I called him ahjussi (old man)," and On Joo Wan was unable to hide that he was taken aback.