Board Thread:Questions and Answers/@comment-10797017-20130622101437/@comment-8986886-20131023132536

Primarch11 wrote: On a side note I feel like Ichigo's Zanpakuto might actually be a Darkness-Type for some reason

It wouldn't be that far fetched, especially concerning his Quincy powers. Quincy use shadows/darkness to travel between dimensions, and when Ichigo used his Mugetsu technique on Aizen, the area surrounding them was covered in complete darkness. There is also the "dark side of the moon" concept to consider, since the name Zangetsu means Slaying Moon.