I need help identifying the girl(?) in the lower picture frame, with brown hair(?). It almost looks like there's a braid, but I'm not sure.

sadodere said:

I need help identifying the girl(?) in the lower picture frame, with brown hair(?). It almost looks like there's a braid, but I'm not sure.

I believe it's Mei.
I wonder where did Cecilia come from? Has she ever worn that kind of hairclips?

Dramorian said:

I believe it's Mei.
I wonder where did Cecilia come from? Has she ever worn that kind of hairclips?

Yes, that looks like Mei. Especially with her braid, I'd presume that's Mei in her black sailor uniform.

The frame in the upper right corner is post #4390922. I don't see the other picture here or on their Pixiv, so I dunno what to say about that.