User blog comment:Silver-Haired Seireitou/Sake Time with Sei - Three's a Crowd/@comment-18812574-20150522051430

Ah, an interesting question. Too bad the blog didn't get much attention, so I'll try and revive it here perhaps...

There are two aspects that must be considered, I think, when we come to this topic. The first are asauchi themselves, the second is Ichigo Kurosaki.

What are Asauchi, exactly? That would help to clarify a lot of what is being asked here. Are they simply dead swords? Pieces of metal that serve as blank canvases to be imprinted upon and utilized by the Shinigami? Obvsiouly not, Afro dude created them, created ALL of them (mostly), and we can assume that the forging process created some very unique forms there. So does that mean the Asauchi were already alive before given to a Shinigami? Yes. This is what canon states, but then that leads us to the problem of Ichigo. (Always he is such a problem child). Ichigo was able to manifest the spirit of a Zanpakuto and even attain bankai without ever actually recieving an actual, well, asauchi. I guess maybe when Rukia stabbed him her sword was transferred onto him somehow? What makes more sense is if he pulled Zangetsu right out of his own soul directly, and in fact that's what happened when he traced the red spirit ribbon back to the box that held Zangetsu's hilt. So there's that. Then the second point comes into play. Turns out Ichigo had TWO powers in him all along, and thus after Zangetsu's "reforging" he pulls out TWO Zanpakuto, and even then there was only one actual asauchi being used.

That being said, if we follow Ichigo's example (which is probably a bad idea) then we can hypothesize that two swords at least means two seperate entities that serve as manifestations of the same person's power. The two powers can be distinct or the same, I suppose. I mean think about how different Hollow Ichigo-whatever-he-is-now and Zangetsu are. You would presume that they would have different abilities as well. (Perhaps no, since it seems the only thing Ichigo can do is Getsuga Tensho, that is). Then there is also Ukitake and Kyoraku to consider. Their zanpakuto were specifically stated to be daisho, the only two pairs in existence in Soul Society or some-such, and in the filler arc those two swords each had two spirits which were pretty distinct from each other. Filler does not contradict canon, however, and still the abilities seem to be the same, so it's hard to say.

I personally think that two swords = two asauchi = the possibility of two different powers. Those powers by nature would necessarily have to be related to one another, although perhaps on a conceptual level more than anything, (light and dark for instance), and whatever the case may be it would be very, very rare. Think about it. A shinigami commits themselves to their zanpakuto and pours their very essence into it. What would happen if they suddenly got a new asauchi and did the same thing? Are relationships that cheap? It would be seen as infidelity, in a way. At least in my opinion. But I'm sure there would be rare exemptions to allow for it. But definitely not often.