User blog comment:Xilinoc/Ch. 642 - BABY, HOLD YOUR HAND 5 (EYES ARE OPEN)/@comment-25162509-20150910104326/@comment-5693502-20150910151819

I think Pernida evolves using the 'left arm of the Soul King'. It's role is advancement, so it would make sense.

Nemu does have a soul (even if it is artificial) so her having a zanpakutō isn't out of the question.