Formerly known as student Beato, by us, who gaslit ourselves into thinking that was a student uniform and then were not able to stop calling her that before finally coming up with the current name.
She is the 19th person X on Rokkenjima, at least in turn and alliance.
She is the most likely to be the the model for the Beatrice portrait.
Sayo isn't X Beatrice
Sayo is distinct from X Beatrice, they are two different people.
Leads:
The Leg Tattoos are too conspicuous of a detail to not be intentional, and they leave no room for doubt.
Beatrice is not "one individual woman" according to Bernkastel.
The two of them interact in the meta layer near the end of Alliance in a way that suggests two people with similar goals.
X Beatrice is the daughter of 0 Beatrice
X was born shortly before 0's death, making her about 19 years old.
Leads:
It works timing wise.
Relatives in anime tend to look really close to each other.
The whole homunculus reincarnation story looks like a very Kinzo way of interpreting a line of hereditary succession.
Battler's has sinned against X Beatrice
It was X beato, not Sayo, who had a coping mechanism that Battler destroyed.
Leads:
The sin is not between him and Beatrice. This could mean Sayo didn't yet identify as Beatrice, but there is a better way of making this fit by saying the sin was actually against X Beatrice, who rejects that role given to her by Kinzo.
She is the one talking to Battler in reality during that scene. She has the outfit and at that point Sayo is probably dead, (although we're not 100% on that).
In the meta layer she is the one with regrets about the sin, and she looks hurt after he doesn't remember.
Shannon 's corpse in legend is X Beatrice
The supposed corpse of Shannon isn't hers and it also isn't a corpse. That is simply X Beatrice trying to hide herself with the help of the adults.
Leads:
We can beat the red by simply claiming that the person there wasn't dead and thus not an unidentified corpse.
Maybe after seeing the girl from the portrait show up the Ushiromiya parents want to keep it a secret in fear for the inheritance.
There's room for a 17th person in Legend.
Obstacles:
Does the motive make any sense with the whole murder going on? Would this be the priority of a bunch of greedy but otherwise innocent people? And are the kids really the ones to whom this secret needs to be kept?
Her presence isn't required for any Legend solution, and keeping the extras to a minimum is part of the self imposed challenge.