So, let me first say that I throughly enjoyed this story, and it is undoubtedly one of my favorites in the Felarya universe. Anko's Secret is an excellent story that gives a much greater in depth look at the daily interactions between a lucky human and a reluctant predator.
Anko's characterization is excellent and is done with a consistency that makes each of her actions believable for her character. I'm happy to have seen such care in maintaining Anko's accent, a bold move by some authors as this is again something else to maintain consistent on. Yet, despite a few hiccups here and there, Anko's accent remains well and true.
Ragna as well is done well enough that his actions around the voracious Anko are believably and don't feel as if they are forced in any way. Ragna is displayed as being rather weak in the knees, but with a strength to stand to the challenge when pushed far enough. He is a warm and likable character that contrastes well against Anko's 'love me hate me' personality.
However, characterization seems to suffer the more the story pulls away from the main cast, as some are nothing more than soap opera villains or carry a naivety about them that suggests they lack the basic wisdom a fully grown adult.
The plot is easy to follow and is done with a practicality that is appreciated. Despite some events occurring that might lack a bit of realism( despite the fact that this is indeed fiction), much of what happens doesn't feel forced in any way, nor lacks the trope of Deus Ex Machina that can typically plague fiction works.
There is unfortunately, glaring errors in the grammar and overall flow in terms of reading that cripple the story overall and ruin the immersion in many cases. Sentences that are worded oddly or in a jumbled way make it difficult to read and times and affect the flow. There are also the errors in grammar in which words are misused repeatedly( ex: course is often mistaken with cause), that are small but blatant errors.
In addition, some cases of the interactions between Ragna and Anko in which Ragna is riding on Anko are worded in ways that don't entirely make sense in some ways or another, or are just not really clear. I had to reread several parts to over to vision properly how Ragna got here or there while being handled by Anko.
Overall, the story is excellent and a pleasant read. While I feel it's main issue is its grammar, it is not difficult to skim over them as it is easy enough to interpret what the author was trying to say. It is an enjoyable work that I think simply requires some fine tuning to buff out the errors that pockmark it.