Btw, I just came across something rather interesting that I had definitely missed in previous playthroughs...
When Ayane is listing names for her future seven children, in her 'Names of Our Children' Event (which was changed during the rework meaning Sel likely added things to it that were notable in the grand scheme of things) she mentions the name "Ai":
Which could be random, but the fact that Ai is notably a name that shows up in the last update:
And seems to be a resident of the Upside Down House:
Likely implies there's some importance to that name in particular.
It also makes me wonder if another possibility for the Shapeshifter's name is Ai?
I still haven't figured out how the other Shapeshifter names are apparently funny to her:
As she notes in Maya's 'Three Halves Make a Whole' Event.
Himawari, Daisy, Sakura, etc, don't really seem all that funny to me. Daisy with the whole "Oopsy Daisy" thing might work.
Ai on the other hand apparently translates to "Affection" or "love", which is something the Shapeshifter apparently isn't allowed to have, due to the rules, which she might find funny in an Ironic way. If not in a cheesy way.
It'd also fit the alliteration naming scheme. Ai Arakawa/Amamiya.
Plus, Sensei thinking of Sunflowers might make him think of Affection or Love, which could lead to the name "Ai".
I'm probably going to add it to the list of potential names, just in case.
Edit: Just to add to this, I'm beginning to wonder if Himawari is more like a nickname for the Shapeshifter, than an actual name. Like, maybe she is her parent's "little himawari" or "little sunflower":