Responses
from how i saw it, child aged joo bin more so admired his brother's friend, and that admiration turned to love as he got older. i don't think the other guy had a thing for little joo bin (that'd be gross), but rather felt an inkling of feelings for him after he'd already confessed to joo bin's brother and went off to the military. at this point i think joo bin was still in high school, which might be why he doesn't want to say it during the truth or dare chapter.
i will admit, though, that the whole thing is kinda strange... but they're both adults in the end so
I don't like the second couple, hope that the author didn't make the pink guy a child while falling in love with his brother's friend. Well, no sane person would even fell in love with a child because that's a child.