Are you drawing comparisons between the part of an update you quoted and the pictures Kana drew that we poked through using RC and the teddy bear?
A few things, including that.
Firstly, yes. Utau positively identified the teddy bear as being Kana's, not Yui's.
"It's Kana's," Utau concluded, giving her a quick smile. "She... loved it, then put it away when..." Utau sighed. "It's connected to the other picture, that's the only reason I'm getting anything at all. It was right afterwards. She didn't feel worthy of it. I'm not getting anything else."
The teddy bear is the hardest piece of evidence to support it, most of the rest are fairly circumstantial.
But to continue- the description of that brown-haired girl from back then blatantly does not match the description of Yui we've gotten in the recent chapters.
A small girl, etched in perfect clarity. A girl no older than five years old, clad in a dirty red dress. Black hair reaching halfway down her back and tangled by neglect.
The girl's long black hair was limp and unkempt;
The impression I was getting was that this is, in fact, Yui's normal appearance. That the one Amu is familiar with has black hair. And yet the one from Kana's memories has brown hair, which is the same color as Kana herself and was older. Now maybe it's just the same hair condition that Ami has and Yui originally had blonde hair that went to brown and then black. Hair color is apparently pretty weak evidence of anything when it comes to this quest.
But the brown haired girl looked 10 and Yui apparently had black hair when she was 5. Amu presumably revised down her age estimate of Yui when she saw what the "actual" Yui looked like, she would have assumed her estimate from the memory Kana shared was wrong.
It might not actually have been wrong. Yui might just not have been wearing the same appearance between those incidents.
Thirdly, Kana's Shadow called Amu "Amu-chan". Akane does not call Amu by honorific:
"Um, happy birthday, Amu," she said, her voice barely above a whisper.
"Amu," Kana whispered. "This is Naomi. Naomi, this is Amu."
On the other hand, Yui apparently does use the "-chan" even if it's "Onee-chan" instead of "Amu-chan". To be fair, this isn't very strong evidence.
Fourth, a meta reason.....
Even with the extra downtime I'm giving you here -- relative to V1 of the quest, which didn't last a single week of story-time, though I'll note right here that there'll be at least a month after this arc before any other major problem happens, and Amu doesn't need to involve herself if she doesn't want to
There's going to be a month of downtime where Amu won't be distracted??? If Yui were still missing by the end of this incident, it's hard to imagine this being the case, since I'd assume Amu would be desperately spending that month trying to find her. It implies to me that we're more likely to get a more decisive conclusion to this, than the hanging thread of a missing Yui.
But the fact is, we're at the "boss fight" now, which makes it feels like we're near the end of the arc. And yet Yui has been conspicuously absent so far, apart from fog and lesser shadows that feel like her but aren't people. There's only so much room left for the real her to make an actual appearance.
Between Yui being an angry and possibly violent incoming pursuer and Yui being Kana's Shadow, I know which one I'd put my money on.
Of course, as mentioned, most of this is circumstantial evidence.
We could be left with the hanging plot thread of a missing Yui. The girl in Kana's memories could really have been Yui, whose hair eventually turned black (or maybe the real one has brown hair and it's just the cognitions that had black hair) and looked older than she was and she could just have been given Kana's teddy bear sometime prior to that event. Honorics aren't much evidence of anything.
It's just a theory that's now near the top of my list at the moment.
