Another interesting angle here is why she thinks we can help. If we don't use the crown on her for something else she might be a direct enough connection to datamine all of Kakuri for information on exaltations. Since she works for Emma-O, her soul is literally in his palace, and she was sent here to get one for him.
The closest possibility I can think of is that she wants to steal one of his mantles so that he has to go to the other to survive.
His backstory does say he started as a god of the Ainu and then started taking power from the Japanese believing he was a demon of punishment. In DF terms that sounds like picking up a new mantle.
How that works with his better half is an interesting question, but assuming some shred is still around crippling or destroying his Emma-O identity in the metaphysical sense could force him to jump ship to a more restrictive office.
Crazy and beyond our abilities, but at least it'd explain what she thinks the opportunity is.
You don't need a large or complex bureaucracy to watch a few dozen people full time. That's the thing. You could easily have three or four devils assigned per akuma and it would still be a meaningless fraction of the Yama King's legions, and it would give you a headsup if they were in trouble and needed bailing out or if they were screwing something up.
Fundamentally, akuma are rare and valuable. The time of the devils required is not.
And yes, sometimes Yama Kings waste akuma because they hate them as they hated their Wan Xian predecessors. That doesn't make them always that stupid or wasteful, particularly not when the akuma are being sent on critical missions.
Not sure I buy those numbers.
Per the ExWoD book, jades are effectively a species and could have spread out over the planet if they weren't outcompeted in various regions. This isn't exactly an actual WoD fusion*, but jades are still a species in the DF too.
Trash mooks can probably be acquired in quantity from the huge explosion in population since the Industrial Revolution.
I can buy a significant percentage of his important elders being here, but I wouldn't be surprised if he had hundreds or potentially thousands of idiots caught before they could get anywhere under his thumb.
There's also the matter of his devils not actually being numberless and their skill sets not being interchangeable.
Four idiots watching one elder Akuma isn't going to do much. Putting four good spies on the same is taking them away from other tasks. They're also more complicated to watch themselves, creating further overhead.
Emma-O has a small country of servants to work with, but that isn't the same as being limitless.
Regardless of how much Akuma are watched on the average, we can make a good guess that the ones on WMD-retrieval will be both liekly watched now and certainly debriefed afterwards.
Which is already enough to make it impossible for Eiko to openly side with us and still achieve her goals at some later point.
Which is why she's talking so unclearly now.
That's a fair point, regardless of mechanism she's going to be high on the watchlist.
Which really blows this whole thing up anyway. She's might be subtle enough to have avoided making it clear what she plans for Emma-O, but she's still obviously screwing around.
I still want to know what she's thinking, but this seems dead on arrival unless Eiko specifically addresses this issue.
* Sort of. It seems like the design goal is to make the ExWoD stuff support the Dresden Files rather than actually merge the settings as peer elements or something.