This isn't a canon I know at all, but I would say you did a fine job of making it readable for unfamiliar folks like me. You kept the named characters down to three to maintain focus on the basic aspects of the plot, so I didn't get overwhelmed with a bunch of unfamiliar names. I'll admit I would like to know a bit more about the Dark Hour, at the same time, I think you communicated the main features of that event throughout the course of the mission, so my lack of understanding is probably just my own curiosity. I don't think the mission suffered at all for that.
I enjoyed the scene where the agents were actively tracking Hamuko with the CAD, and we got to see the character fluctuation change in real time. It gave an element of fluidity to the moment, rather than just being a series of numbers interspersed throughout the mission. I also liked the planning stage at the end. Even though roping canon characters into helping the agents isn't standard, I think it's appropriate for agents to recognize when they're outmatched, and to use the features available to them in the canon. Valka's bonus Medical trap for Elena at the end was a fun surprise, as well. I liked that the agents got some downtime to spend at the arcade, even though it was partly foreshadowing what was happening to Elena. I like it when missions cause personal roadblocks for the agents, so having Elena get charmed by the poisoned cookies was a nice way to impact the agents' functionality in an on-theme way, even though you engineered the event out of whole cloth.
One section that stood out as confusing was the conversation the agents had in their RC before the mission. Discussing the Persona series segues into talking about shape-shifting species in Fire Emblem, and I don't understand the connection between the two topic threads. It feels like a very abrupt change to me. Am I missing a connection between the two topics?
Finally, some typos Hieronymus Graubart missed (But he caught some I missed, so we're even.):
"Valka didn’t want to hurt her partner, and that meant being gentle, but it also meant not going to love hotel with someone clearly under the influence of something."
"to a love hotel"
"'Elena, listen to yourself!' Valka said back "
(No end punctuation here.)
"She could reasonably call the wraith possessing a Hamuko a special kind of shadow, which wasn’t too far from the truth."
An extra word.
Also, I wasn't sure about "charmdi" in the one CAD readout. I suspect it's a canon thing, but I wanted to point it out just in case.
—doctorlit beneath the mask