- Back in Volume two, when Yuko had folded a butterfly to track someone, she mentioned that if it had to travel farther, it would need to become a bird. The symbols that represent Yuko and Watanuki are a butterfly and a bird respectively. Watanuki isn't just a replacement of Yuko, he's her successor through and through, and one day he'll be more powerful than she ever was.
- Yuko appears to find Tanpopo's form appropriate once she sees it for the first time. The little bird was born thanks to Watanuki's wish to make Himawari happy. He literally gave something of himself (i.e. his symbol) to her.
- When the series gained the tagline "Rou" (meaning "cage") it was obvious that it referred to how the shop had become a cage that Watanuki was trapped in... but then he really became "the bird in a cage" when he decided the bird would be his symbol.
- The Faceless Masses. The fact that people outside of the main cast and Yuuko's customers are always depicted this way foreshadows that Watanuki can't remember the faces of anyone else. This is how he literally sees them.
- Yuuko has probably seen Watanuki die hundreds of times because of the stable time loop in Tsubasa Reservoir Chronicle