User blog comment:Xilinoc/Ch. 626 - THE HOLY NEWBORN/@comment-24531362-20150514204604/@comment-11051098-20150515183859

I don't think your theory is impossible, but I think Yhwach is too confident in his own powers to even consider his own defeat, and as such, no reason why he should bother holding a Shinigami lieutenant captive to use against the Gotei.

Your first point could be true though. Gigi could indeed have zombified Yachiru at some point during Kenpachi's fight with Gremmy, to use her as a pawn. If so, the question is how things would develop from here on.

If Yachiru should turn out to be a zombie under Gigi's control and Kenpachi got to know... well, Gigi could be up for some trouble.