Ichigo sighed lowly so his teacher wouldn't hear it. I figured you'd say that. I've actually been a little curious about something, actually. If you're a Hollow, why don't you look like the other Hollows? Almost every Hollow I've met was mostly black with only a white mask, and most of them had lost human shape. And I've never seen your Hollow hole.
Because I'm not exactly a Hollow, King. The demented white version of Ichigo sounded rather serious for once. Before you regained your Shinigami powers in that pit, you first began becoming a Hollow. So when you pulled Zangetsu out of that box, you had both Hollow powers and Shinigami powers, but the Shinigami powers took precedence as you stopped yourself from becoming a Hollow, so you got Zangetsu in your Inner World.
Ichigo was getting impatient. I already figured most of that out from our previous conversations, but if you're not a Hollow, what are you?
Can you not figure it out, King? Zangetsu is our Zanpakuto, but he takes another form in your Inner World.
You are my mask, Ichigo realized.
Bingo! Hollow Ichigo cackled. What you are, Shinigami or Hollow, depends on who is in control – you or me. A soul truly becomes a Hollow when the mask takes over.