Neko no ongaeshi and Mimi wo sumaseba is the example of how a story within a story is intriguing enough that it gets an adaptation on its own I had tried to work on a story within my story several times, and voila, none of them finished
Speaking of Neko no ongaeshi, now that I watched it again, it feels like a great example of your first work that you wrote in teenage years. It feels a lot like teenager's way of writing fantasy, but then edited in later years without changing much.
It feels really nice to watch it again, though, because it's one of my favourites simply because it's simple, nice, and light, but the structure is good.
I had tried to work on a story within my story several times, and voila, none of them finished