User blog comment:Xilinoc/Ch. 668 - BIGGER,FASTER,STRONGER/@comment-1268838-20160331160224/@comment-28861328-20160331165718

So you're okay with:
 * Yachiru being the Spirit, despite the fact that Zaraki called his Zanpakuto a "he" back in the Arrancar?
 * The fact that Yachiru herself had her own Shikai, completely unrelated to Zaraki's, which was shown just a few months ago?
 * The fact that, in order to acquire Shikai, one must communicate with and learn the Zanpakuto's name, yet Zaraki asked Yachiru "what [she's] doing, clearly confused on what she's say; which would suggest he had never met his Spirit before?
 * The fact that, to even properly use a Bankai, one either has to train for 10 years or use Urahara's special method, yet Zaraki is being handed his, not long after acquiring his Shikai, with no training and no preparation whatsoever?

Those are just a few holes that this would blow into the overall narrative if Kubo goes through with that idea. It's bad writing, plain and simple. Of course, the next chapter could reveal that there is nothing to this story and that Yachiru isn't the Spirit; but if she is, Kubo is really insulting his reader's intelligence here.