Board Thread:Improvements and Issues/@comment-1409915-20140307195609/@comment-26091912-20150616131120

We don't know Yachiru's release command, either because it was spoken off-panel, or her Zanpakuto was already released prior.

Her release command couldn't be "C'mon out", because Guaneel was attacked with the shikai special ability before she said that. So either Sanpo Kenjuu is a full-time release like Zangetsu, or it's shikai abilities don't dissipate after sheathing her sword, like Ryujin Jakka. It's possible that she doesn't have a release command, and can bypass it altogether, although that's unlikely. It can't be a full-time release, because her spiritual energy isn't that powerful, and she also seems to have pretty good control over it (considering she's skilled at infiltration).

As for the theory that Yachiru is the Zanpakuto spirit Nozarashi, well I'm sorry, but it's bunk. For it to even be plausible, you'd have to throw everything that's been established about Zanpakuto out the window. Zanpakuto facts aside, there are many indications that this cannot be the case: 1) Kenpachi was in Muken when he heard Nozarashi calling to him, Yachiru was nowhere near Muken. 2) After Kenpachi fully released Nozarashi, Yachiru was still there recalling their first meeting. 3) Yachiru's lieutenant badge didn't disappear, yet she along with the rest of her uniform supposedly did. (When Starrk released his Resurreccion, even Lilynette's sword disappeared).