Morning reblog so you may all witness his glory. And some more lore;
This isn't even the weirdest Kami I put in the fic.
That's probably Wax Mallow.
When Mimihagi first took up residence in Ukitake's body, the boy was still very young and, not wanting mess the little creature up more, Mimihagi invented the spiritual equivalent of a hand puppet to talk to Jushiro on his dreams, not unlike how baby condors raised in captivity are fed with a condor puppet so they imprint on the right species.
To Mimihagi's vast surprise, humans love playing make-believe and young Ukitake invented a puppet of his own that was the first puppet's twin and daydreamed adventures for the two fictional boys all the time.
Between the God Powers and amount of his soul Ukitake poured into them, these puppets eventually became the Twin Fishes that make up Ukitake's zanpaktou.
Mimihagi finally reveal-revealed himself when Jushiro hit adolescence and was playing less and less, not because he didn't want to play, but because he was busy being a human person and Mimihagi felt like he ought to be honest with his young friend.
Jushiro had long suspected that the invisible friend he had was different from everyone else's, not least of all because he didn't vanish with age, and while learning he had *An Actual Factual Kami* inside him made Jushiro worry a bit about the stakes, he was never frightened of Mimihagi.
Actually, a bit of world building: I'm AEIWAM, all souls are actually two souls: a soul that controls they physical or spiritual body, or iekon or "host soul" and an inner spirit with a less-defined amd less stable form called a Naikon or "guest soul". The relationship between these two is mutually beneficial: the iekon gives it's inner soul a stable metabolism and more coherent mind- a safe place to live. The Naikon gives it's host spiritual power/fortitude and helps protect the host in times of distress.
Like if your fursona was also your gut bacteria.
Naikon and iekon both spawn in the living world and as soon as an iekon is developed enough to host a naikon, it starts making a spiritual heartbeat, and that vibration draws a compatible naikon to them, and the two bond shortly before or after birth/germination/hatching.
All souls, even birds, trees, and major spirits, have a bonded inner soul.
A shinigami is someone who has managed to consciously communicate with their naikon and bonded it to a tool that allows them to cooperatively wield enormous amounts of energy safely.
Ukitake's root medical issue is that he was born without a naikon. Extremely rare and usually fatal even before the child is born. Ukitake is a tough little shit and clung to life with white knuckles until he met Mimihagi, and the Kami agreed to be his naikon.
Mimihagi was VERY lonely.
Mimihagi stops the damage being done to Ukitake less with his power of stagnation and more with just being in there, but as a Kami he has Kami Stuff he needs to do, and so whenever he has to divide his attention, Jushiro essentially starts degrading again until Mimihagi returns.
Mimihagi cannot heal the damage, only stop it from getting worse, so it's a damn good thing Ukitake knows Unohana. She does her best but really, Jushiro is her only known case of this* and she's kind of winging it. One thing she's discovered is that Mimihagi's presence protects Jushiro not just from further degradation, but also damage from additional injuries and toxins, like an auxiliary liver and immune system.
*in the second act, her practice with Jushiro is ESSENTIAL to their victory over Yhwach and the Quincy.
This makes medicating Ukitake tricky because she effectively has to medicate Mimihagi past the point of his protection first before the drugs ever reach Jushiro.
Consequently Ukitake has never been drunk, but he takes enough ketamine every morning to actually kill a horse, and Mimihagi is often HIGH AS BALLS.
In the extras it says Ukitake's favorite food is Ohagi, but in AEIWAM, *Mimihagi* is the one that really likes Ohagi, because they're a traditional shrine offering, and Ukitake developed a taste for them after the fact.
