User blog comment:Xilinoc/Ch. 541 - THE BLADE AND ME 2/@comment-9282993-20130616200156/@comment-10630156-20130616232742

The arch with Muramasa was a filler arch it was not in the Manga As for when he was training Ichigo Hollow Ichigo was always there and they are BOTH part of Ichigo's power so why wouldn't they be able to fuse. The Yhwach-Zangetsu is Ichigo's inner Quincy and this is probably how all inner quincy are as Yhwach was the first quincy and all quincys come from him. I doubt that he is exactly the same as Yhwach