Gotta say, I don't really care about the twintails girl messing around with the other guy. MC really hasn't expressed any interest in her from what I remember, she's just pining after him.
I cared more about the other girl on the island during the reality show, because at least then her and MC actually had a mutual attraction(even if Sakura is his main focus).
Hell, I cared more about the idol group getting taken advantage of by the skeevy old guy manager than I care about twintails girl.