If Paper Heron ever gets an anecdote, I 100% want it to focus around her, Eternity, and maybe a few other long-lived characters like Lucy discussing how their long lifespans have affected them.
The different ways Paper Heron and Eternity each approached their own immortality is really interesting to me. They're practically on opposite ends of the spectrum.
Paper Heron is a homeless vagabond wandering from place to place, living humbly and never throwing her status around. She goes with the flow, going along with whatever life throws at her like a leaf in the wind, cherishing the human connections she makes even if she knows she'll have to part with them eventually. She lives in the moment at all times despite the long life ahead of her.
Meanwhile Eternity is a city-slicking socialite who surrounds herself in material luxury. Beautiful things that are monetarily valuable but emotionally worthless. She shuns human connection and even higher art, preferring superficial and fleeting trends. Because if she allowed herself to indulge in the irreplaceable, it would hurt so much more when she has to see them fade away. Fleeting but easily replaced things are the only things that can remain a constant for Eternity, who deep down craves to hold onto something that can be as eternal as she is.
Paper Heron can be that something for her I think. Not even as a romantic partner or anything. I think they'd be good friends for one another, assuming Paper Heron doesn't disapprove of Eternity's swindling too much.
Paper Heron can help Eternity open up more thanks to her being a fellow immortal while Eternity can help Paper Heron keep up with the modern world.