|So I went back and was reading Aizen's confessions to Ichigo (just before getting the Hogyoku and leaving Soul Society) and he refers to Urahara as being exiled for his Gigai creation (specifically non-spiritual matter material bodies he created). |
Later when Isshin defeats the Grandfisher Arrancar he talks to Urahara about never finding the Vaizard group.
Sadly I haven't been able to read the TBTP Arc, only watch it in the Anime, assuming it is faithful to the Manga:
Tessai, the 8 Arrancar, and Urahara all leave at the very end. Yoruichi stays behind, telling Tessai that she can escape when she feels like it. This was the day after he saved Hirako and co. from Aizen and was accused of experimenting on them.
I think that was used as a cover up or something like that... the gigais I mean
|all of that we know that Isshin left sometime after this, what's more is that he left at max 40 years ago. Assuming that Masaki was young (14-15) and that Ichigo was born when she was in her 20s or 30s and is now 18 (at most, he started at 15 and some timeskips for the Xcution and current Quincy Arc) we get 10/20+18 for a max of 38. And that is assuming that he left Soul Society before Ichigo was born. It's entirely possible that he was still in Soul Society the day Masaki died, hence his regrets.|
Isshin says to urahara that ''grand fisher'' is a different type of arrancar from the one he fought 17 years ago(at the time of Ichigo's encounter with hirako) so Isshin and masaki met at least 2 years before Ichigo's birth from what I remember... But I'm not sure of the fact that isshin went after Urahara since I'm pretty sure that Kaien would at least mention the fact that his relative is a captain of another division of the gotei.. And on that matter I doubt that Isshin was a member of a branch family of Shiba since from what I know of history and how main vs branch houses work it was always made impossible that a branch family member exceedes a main family member in power/rank so I'm more inclined to believe if anything that Kaien, kuukaku and ganju were member of the branch or even(what I would prefer) that they were all members of main family..