OOOOOH I FOUND THE CHAPTER, the convo went
Jeongwon: 'Why did you suddenly have that thought? "
Haewoon: "Well because Jeongwon, you—
That...
You correctly guessed our song during that music quiz."
JW: "That... I told you it was because my friend practiced it for a talent show."
HW: "That may be so, but honestly, it doesn't make sense."
JW: " What doesn't?"
HW: "No matter how hard that friend prepared for the talent show, I would have practiced more than them, yet even I couldn't guess it after hearing just a little bit of it. You even said you weren't the one involved, Jeongwon, just that you heard it from the side.
And who on earth is that friend? Were you that close to them? Enough to remember it clearly even ten years later? Do you still keep in touch? Is he a better dancer than me?"
JW: "Haeun, what kind of nonsense is that?
(Idk why but the translated novel actually changes haewoon's name to haeun)
Of course you dance better."
JW: " Right?"
Lol I've read the novel and at this part it was so hilarious the convo went like
Jeongwon: how did you come up with that?
Haewoon: I just think that, so are you a fan?
Jaewoon:what makes you say that?
Haewoon internally: why is he not telling me? Is it hard to tell me he is a fan?
Something like that. But anyways he ended up saying yes and haewoon pestered him like crazy.