This book is called “Himawari.” (Sunflower)
Rather than going horizontally, the pages turn vertically, thus allowing the sunflower to grow on the pages.
Sunflowers are not super common in Japan, I don’t think. I come from the Sunflower State, Kansas. Sunflowers are a huge deal there. Nevertheless, one never just comes across a huge field of sunflowers by chance. When my husband lived there, he and his fellow Japanese friends sought out a large sunflower field and took photos there. The crazy things foreigners do!
This book is available here.