The only lacking aspect is Story Development and World Background. The reason why I have rated Story Development and World Background lower is because the fanfiction relies heavily on an already developed story and world, as you know, because it is a fanfiction.
I feel rating that as 5 is a bit silly, considering that the general story is not actually a work of the fanfiction author.
As for everything else, it checks the 5 star mark for everything. I am very surprised this fanfiction is not that popular on this site, it is very popular on the Fanfiction.net site, the grammar is basically perfect, the development and design of the OC main character and the development of already established characters was very well done.
When it comes to Character Design for fanfictions, I base it mostly on how well the author can keep the personalities and characters intact, how well they can write dialogue that would be believable in the original creations, in this case, the original Touhou games. 5 Stars for Character Design/Development
In general, I enjoyed the fanfiction a lot, even though I had never played the Touhou games. Throughout reading, I frequented the wiki in order to understand the story better and the characters, but obviously, this fanfiction was not aimed towards people who have never been introduced to Touhou before. Even then, I REALLY enjoyed the work done and found myself giggling like a little boy at certain parts. The fanfiction can at times be heavy, at times sad but most of the time, it is all a good laugh and is incredible interesting.
Once the current arc finishes, I will definitely hop back into this fanfiction and continue reading!
