Yeah, I knew it was unlikely for anyone to partner with a spirit from the start like Grian does, in fact my first idea for this was "episode where xB gets possessed by the spirit of Hiding or something and plot twist the episode doesn't end with him defeated, the monster is invisible by definition and after its conflict is done it can't be caught, plot twist xB stays like that for the rest of the season peacefully somehow, I guess that could mean somehow being a full magical girl who's just undetectable instead of having a transformation sequence, this could also power up his ability so Scar eventually forgets he even has that guy to look out for..." and then I couldn't think of any situation where a character whose whole plot point is staying hidden would do anything to cause the heroes to notice it enough for an episode to happen anyway, and then I imagined that first burst of all of them escaping, off to do various chaotic things, and then the one that's based on some concept that's naturally peaceful and quiet all along just calmly floats along until it finds someone who's used to being quiet and would be happy to be rid of what little attention he does get, so I thought it would be funny if the two just met and instantly agreed fully or however partnership works, like before the monster attacks have happened enough that xB even knows about them, you know?

That plus the "mysterious helper who may or may not know all the secrets but either way ends up not being a threat" trope and the "unremarkable background character with an inexplicably dedicated fandom" trope, it would work just as well to have him start appearing at any time but it feels funnier/more fulfilling to be able to look at this imaginary anime and have at least one frame of every single episode where he's visible!

oh hmmm that's actually a fun one. and to be fair, i think xb would be... rather happy to slip into the background, honestly. sure, this is all... a lot more than he'd prefer to deal with. but watching scar's crew deal with it has given him SOME idea of how to handle the fact he still has a spirit around, and being able to be invisible sometimes... it's useful. it's useful!

i think maybe he shows up in the background of some support group episodes afterwards and if you aren't paying attention it's hard to realize what's happening.

however i'm honestly still not sure how early in the plot we can have a spirit partnership here? i think maybe. xb is an early possession victim (maybe one of the first ones blackbird interferes with?) but the spirit escapes. xb sort of just slips away without letting anyone help him quietly because he manages to get unpossessed but he just KNOWS people are gonna be weird about the fact the spirit escaped. plus, he has unlocked a little more of his magical potential now. he can just... make himself disappear. he doesn't know why. it's not a partnership, so much as a potential he already had that, like a few other members of the plot (bdubs being out big example), due to a combination "wishing star getting closer" and "spirit possession", he can do even more.

and it's... nice. sometimes it isn't nice - he basically can't go out to eat unless he's with someone else, the waitstaff will forget he's there, and actually for anything he needs to be remembered for it's kind of a pain, but in a lot of life he just... slides in the background now. and if he really, really wants to be noticed he can mostly turn it off? but eh, he's an introvert anyway, as long as his small circle of friends still talks to him, he's fine. keralis and hypno and beef haven't forgotten he exists yet.

(hypno nearly forgets once. it makes xb's hair stand on end. he puts more effort into his side of the friendship with him for months afterwards. hypno's bemused. "you never texted back so quick before. what's gotten into you - monsters making you remember your mortality?" and it's... easier than the actual answer to go with that. hypno says xb should go to the support group again. xb doesn't say: they won't remember i'm there too if i don't make an effort to talk the whole time.)

its later in the plot, after... i had a timeline somewhere, but i think at LEAST after bdubs joins the squad and DEFINITELY after the "the magical girl crew fights the military" incident. it's then that the spirit of hiding reappears, and, drawn once again to xb's magic, despite the fact he's arguably more resistant to possession now, turns up where xb is.

and like... look. xb really, really doesn't want to get possessed again. because as nice as fading into the background is, he just... he doesn't want...

and they find themselves at an impasse.

xb gets this guy, is the thing. compared to other spirits, this guy doesn't do that much. it just... makes it easy to forget itself. to forget other people. and there's a horror in that, too, but there's also... xb can relate. before all of this started, he would have thought he'd be content to be entirely forgotten as well. it's just, the brief moment when someone he was close to had no recognition in his eyes -

"hey," xb says to the spirit that does not want to leave but that he doesn't want to let possess him. "hey. change of plans. how about we make a deal? i think there's something we can both offer to each other."

two days later, he slips into keralis's door and, once he finds the man, quietly sobs. he never says why. afterwards, he goes back to almost-normal. almost. if you aren't one of his friends, at least. his friends are... concerned. he's up to something.

xb assures them: he won't interfere that much. not his style. also, if he WERE to get noticed, he's pretty sure he might get dissected or something? so. much better to just... adjust from the background when he can.

he's sure it'll turn out fine.