It's strange, but they never notice, no matter how much time has passed. If one girl wants to catch the other's eye, she's looking somewhere else. Even when she's putting all of her effort into it, their thoughts never quite coincide. But that's part of what makes their balance perfect.
Mysteriously, no matter how much time goes by, they don't notice. Whenever one seeks the other's glance, she's always looking at something else. Even now, when you could say she's putting her all into something, their thoughts do nothing but cross, but that's their miraculous balance.