The mother tells the girl she is baking a cake for when she returns. The girl waits. The cake never comes. In the final chapter, Rosalina (as an adult) realizes the cake was a metaphor for love—it was always there, even if never eaten.
While there is no "official" free PDF provided by Nintendo, you can access the content of Rosalina's Storybook (the emotional backstory from Super Mario Galaxy rosalina s storybook pdf download upd
The "Luma" and "Rosalina's Storybook" themes are fan favorites for their lullaby-like quality. Why Fans Seek the PDF Version The mother tells the girl she is baking