thinks about. sonic post-metal virus arc believing he's still infected
he avoids touching others like the plague. he feels the virus crawling on his skin, slowly consuming him even after he and silver purged the world of it. at night, instead of sleeping, he runs to "burn the infection off". he's constantly restless and has to be forced by his friends to rest properly, if they can catch him
no amount of reassuring him he got rid of the virus helps. he just doubles down, believing it mutated somehow, or that he missed some when they got rid of it. only thing that gets him to settle down is scanning him for the virus with the miles electric (or gemerl, if he's present). he figures "maybe *they* can't see it, but a machine will detect it for sure"
i imagine the first time it happens, he's still in the sol dimension (in the version of canon that exists in my head, there was no amnesia plot. just an... impromptu-forced vacation, basically). blaze doesn't have the tech needed to scan him and assure him it's truly gone, so instead she "burned" the virus off using her flames. she didn't really burn anything, just made it look like she did to calm him down
having her "burn" the virus off him and getting gardon to keep watch while he slept was the only way he felt safe enough to rest while he recovered enough to make the trip back to his dimension
after a while, the thoughts begin to subside, and he learns how to ground himself whenever they come back. but there's always still a part of him, deep in the back of his mind, that believes he's still infected
i imagine the cyber corruption from frontiers caused him to fall back into that belief for a time, since it felt so similar to the virus. cold, tingling numbness on the skin, permeating deep into the flesh and bone, isn't exactly a sensation a perfectly healthy person feels on the regular
