That’s not just any flower petal, that’s a cherry blossom. Or as the Japanese call the tree, a Sakura… and the anime that opening is from is titled (you’ll never guess it) Card Captor Sakura! Google-san tells me this about Sakura:
The blooming of these legendary trees represents a time of renewal, feminine beauty, and the fragility of human life.
I think that probably covers it in a nutshell. Those sorts of themes are definitely on-point for a magical-girl anime.
