She just drifted right into her fantasy bliss, how adorable. And buying nail varnish for her? He's growing up.
@starburst98 it's to do with the differences in play between groups of boys and groups of girls (in cohort). For girls, participation is often the most important part of play. For boys, it is moreso competition that provides the entertainment. The girls were playing completely honestly because winning isn't important, playing together is. Ouji was playing competitively, because for him, potentially winning is the reason to play a game.
It just highlighted how he seemingly comes from a different universe, and neither the girls nor Ouji knew how to bridge the gap even with honest intentions.