Very very dumb Bleach AU idea where Ichigo(at full power basically soul king level) goes back in time to fix everything ends up way further back like young captain commander time, he's able to fully kill Yhwach and prevent him doing anything at all, no sleep no future quincy war, he also gets involved in making soul society...more so just vetoing anything like central 46 because nothing involving them ended well, and should make things easier and less likely for anyone to manipulate.
He travels around for a bit making sure everything settled and no other persons gonna try to take over the world before not really knowing what to do... when he next checks in on soul society gotei 13's all established and everything seems to be going well, but when he checks in on captain commander he's like 'Well we need someone in charge'
'Isn't that you old man?'
'I can't be fully in charge of all of soul society I run the gotei 13... no we need someone else to run soul society'
'...'
'...no'
Ichigo is now on the run from all the captains who are trying to get him to take over things because a) he's insanely powerful b) he's actually good and not corrupted and will actually care about people and not just the nobles c) He has common sense.
'DON'T YOU HAVE THE SOUL KING FOR THIS?'
'Ichigo I am still convinced you are the soul king'
'I'm not!'
'You haven't aged a single day in the hundreds of years i've known you and you literally bitch slapped Ywatch into oblivion, you also seem to have all the powers..ALL OF THEM'
'...I...I...I mean your wrong... bit I do get it'
And this goes on for centuries Ichigo tying very hard not to have to rule soul society and convince people he isn't the soul king. Only her keeps ending up doing this because he keeps ending up adopting younger versions of captains and others. (It started with the captain commander sending little Jushiro, Kyoraku and a tiny feral Unohana to stop Ichigo he just went big brother mode... he is the one person Unohana will listen to and not try to murder...well when she tries to murder him it's more a game then an actually murder attempt)
Just Ichigo who ends up being big brother to like all of Seireitei, he doesn't age at all but even when the others get older them him still totally see him as their big brother. Him always having at least one or two following him around like ducklings.
Some hollows figuring out how to evolve to arrancar naturally... Ichigo was in Hucheo mundo for a while and his weird reality breaking powers might have affected things. Shinigami are totally chill with them because all of them have seen these types of hollow powers before most grew up seeing Ichigo use them casually. (Also Unohana wants to fight them)
Well until Grimmjow shows up and him and Ichigo are fight flirting just being very weird and all of seretiei are ready to give a shovel talk. Captain meetings are them plotting 'Big brother can do way better'. Captain commander is just watching all this amused.
(None of them realize Grimmjow thought process is
'Wait if I date Kurosaki I get to fight all of them... OI KUROSAKI WE'RE DATING NOW!'
'...WAIT WHAT?')
