u/Divinum_Fulmen

The word for shut in is

引きこもり [ひきこもり]　(hikikomori)

But that's almost the same as

匹蝙蝠 ひきこうもり　(hiki koumori)

Meaning a counter for small animals + bat, or "a bat." So she's a "hiki koumori," or a bat.

It's missing a number and particle to be good grammar in Japanese, and her artists commentary doesn't mention anything, but it seems to funny to be a coincidence.