Has anyone adopted this, I wanna read more of it

Heck, I'm willing to adopt it although I'm not sure when I would be able to get around the writing it since I already got two Kaien/Ichigo stories that I am working on at the moment. Funnily enough for one of my stories I ended up going with the 'chunk of Kaien's soul joins Ichigo's soul' idea.

Love the idea of the Hollow actually being Kaien. That's incredibly creative. Wish I had thought of that.

I really like this premise but I do think it is all very rushed/forced. You should've spent more time creating the atmosphere this kind of revelation deserves. Also Nejibana's personality doesn't match her title of strongest water-type zanpakutō. Her mermaid outfit makes sense but you could've described her as something other than "curvy in all the right places". She sounds ditzy and shallow. As a zanpakutō she is supposed to mirror Ichigo's soul and he is anything but that. I hope I'm not sounding too harsh it's just that I see a lot of potential in this. As for pairings, gen is better if you want to focus on some form of plot and/or the power of being nakama.

This is a really interesting idea! And making hollow Ichi turn out to actually be kaien makes sense in a strange way

Looks like a great story please continue. The pairing should be rukia and yoruichi by the way

This ist a great Idee, keep writing.

Well, that was a surprise.

i think that in the future you should mix the powers of Nejibana and Zangetsu since we know that he will regain his own spiritual powers especially since Mugetus in my undestanding is very similar to the Letz Still which means that both can be restored so i think that you should you fused version of Ichigo Zangetsu and Kaien Nejibana meaning that from their fusion a completely new zanpakuto will be born meaning that he will still be the same Hybrid(SoulReaper,Hollow,Quincy) just stronger(better control, bigger reserves,ability to use kido etc) and about the pairing i would like to see Ichigo x Neliel x Rukia thanks