I think that those two will actually be the main couple by the end. The idol is going to think that they have something going on (because pig-tail girl wants to keep an eye on MC, classic misunderstanding), so she tries to nudge them together, and the two end up together by the end. Not only would this be an interesting plot, but part of me thinks that this is what the cover is implying.
Yes, it's a wild prediction, but I can see it happening. The only thing that makes me think otherwise is the title of the manga, but we're still pretty early on, so not enough to say for sure.
@Bistai honestly this is how i wish the plot would go, but you never know... crossing my fingers tho! i must say pigtail girl is more interesting to me than the idol, who looks very cute but?? yknow. way too perfect with no flaws.