I have been negligent in my duties as your Enabler. Here is an idea: Erich is a cat person. He is thus somewhat discomforted by Yoruichi's presence - although fully aware that it is a fully cognizant shinigami, he has to bite down the urge to pet the pretty cat.
The first time Erich meets Yoruichi, he doesn’t realize she’s a Reaper.
She’s sitting atop a side table, watching him like cats are wont to do, and seems... perfectly normal. No reiatsu, no odd movements or talking. She’s just a cat, sitting on a table, and Erich is desperately in need of a way to calm down.
(He loves cats. They’re perfectly capable of caring for themselves if necessary, but they’re also incredibly loving. They can be very relaxing.)
He approaches her and offers his hand, waiting to see if she’ll accept his attention.
(He needs something to ground him. Some way to keep himself from fleeing the shoten in the face of what he’s just done. Outing himself as a Quincy to a Reaper goes against EVERYTHING he’s lived with, even if this Reaper is not precisely part of Seireitei anymore.)
(He’s afraid, and a hairsbreadth from panicking, and the only outward sign is the fine tremors in his fingers.)
He doesn’t want to remain in the shoten any longer, doesn’t want to remain around the Reapers any more, but he NEEDS to be polite, needs to stay to speak, to at least start to work out the awkward truce that he and Urahara are starting to form for the sake of the teens.
The cat accepts. Erich breathes out a sigh. Tries to relax.
Urahara walks into the room. Squawks in protest at Yoruichi, who /snarks back/.
Erich freezes, steps away. He still can’t sense her, but that’s a TALKING CAT, which DEFINITELY means it’s not a normal cat. And without a hint of reiatsu, it means she’s probably a powerful Reaper herself.
(It’s a week before anyone but Uryuu sees him for more than a few minutes at a time. Erich is wary and waiting for the other shoe to drop, waiting for the Reapers to come to attack him, waiting for the repercussions of... everything.)
(By the time the edge of his fear has settled, and he can approach the shoten without nearly having a panic attack, Erich has firmly settled Yoruichi into “do not touch” territory. Even when she tries to get him to pet her, he doesn’t.)
(Yoruichi is actually a bit disappointed by this. Erich gave GREAT scritches. She just... ruined her first impression. Damnit.)