Basically, when I was in bed a random thought occurred to me.

There's an old movie/franchise called The Crow, which was based on a comic book -- while there are some key differences between the movie adaption that spawned the media franchise and the original comic book, such as the crow animal itself being a spiritual being that can't be seen or interacted with (compared to in the movies where they can be seen/interacted with by everyone, and they act as points of vulnerability for the Returned), they pretty much all line up with each other.

Basically, those who were unjustly killed/murdered et cetera have their souls carried to the afterlife by a crow, but if the soul has regrets/anger, they can't pass on. A mysterious entity basically punts them, as avatars of justice and revenge for their own situations, back to the living world so they can get justice. It's not known what entity does this, if there is one at all, but it being a god-like entity like the Crow Girl (and her suspected identity) could easily be a thing.

My mind basically made the connection between a Crow's return and Ai's death.

The (unreliable) Crow Girl recently said that Ai had "no regrets" when she died, and that "she thought no more" because she'd "dissolved/become one with the ocean and stars", but I find that hard to believe, to be honest.

Yes, she finally realized that she could love in her last moments after being stabbed, but her regret would be that she wouldn't be there to see Ruby and Aqua grow up and be a mother. I guess canonically that wouldn't be strong enough for her to reincarnate like Ruby and Aqua, but...

What if another entity, unforeseen by the Crow Girl, stepped in at the very last moment of Ai's death, Being X-style (I don't mean as in the actual Being X from YS, but the style of appearing to her in her very last moment stretched out into an eternity to talk with her)?

That it not only manipulated her by fomenting the feelings of regret in Ai, but it also stoked her anger/fury at the one responsible for her murder by revealing his identify/motives/future? That he was the cause of Ruby and Aqua becoming orphans? That anger and grudge would remain and fester in her soul until she was ready to return to the land of the living...

Sixteen years later, Ai Hoshino crawls out of her grave on a stormy, wet night, and perched upon her own tombstone and watching her with gimlet eyes was a simple, unremarkable crow...

Also, I could see Crow Girl noticing the "odd" crow in question sometimes and being confused. "That's not one of mine", and over time she begins to realize that something in her plan has gone very, very wrong as another entity like herself is moving behind the scenes (could be a small subplot where we see her trying to piece together things, as she's just in the dark about what's going on, too).

Ai sadly looking on Aqua and Ruby at a distance while she goes around getting her revenge/justice would be heartbreaking, especially if the two (especially Aqua) keep almost catching her/uncovering what's going on.

Ai meeting with and talking to Miyako one night in her apartment would be amazing.

"Ai? You're alive?" (sees the black and white makeup and a very dead Ai talking to her from the window) "Oh." Her keeping this secret from the Twins, and their knowing something is up and it's causing a small rift, could be a great subplot.

The Crow Girl unintentionally causing the crow avatar to go from just a spiritual being only she, Ai, and Hikaru could see/interact with (such as in the original comic book) to a physical weakness/entity anyone could interact with (the movies and other media), and realizing that she basically fucked up by doing so, would be a nice twist, too.

I dunno; maybe I just have too much time on my hands, heh.