I love this. For me, right now in my life, my ikigai is Storytelling.
I engage with it in every aspect of my life (and all four of the Big Circles in the diagram), and trying to describe the feeling I have when I think about it--it's so hard! I would say that it "fills me up" but that isn't quite right -- it more makes me realize that the well of happiness inside me is not finite (which is something I believed for a long time), but in fact infinite. And the idea of never being able to fill it is not scary because now I understand it isn't something that's meant to be filled, it's something that's meant to be explored and discovered anew every minute of every day, and the potential for doing so is in fact, infinite.
Ugh, for someone who claims to be a writer that was pretty shoddy. I guess I am still exploring what this means to me!!!