Can you see the story the more you put it? I found a nice bookmark at the 100-yen shop "Daiso", so I will introduce it.
The "Silhouette Index" is an index sticker that can be pasted and peeled off in the shape of silhouettes of various motifs. At the store I went to, there are three types of "ballet," "safari," and "amusement park," each containing three seats.
When you put it on the page you care about in the book, the index that pops out spreads like a landscape. Since it is a silhouette, it does not stand out too much and can express a casual playfulness, so it may be used as a notebook or a document to give to someone.
It is thicker and more adhesive than film sticky notes, and it is hard to peel off when you pinch and open the page. Why don't you put it on various places and have fun?