Gosick (2011) IMDb
There is a francophone country the size of Corsica nestled between Italy and France, seemingly just a mile or so east of real-world Monaco. This country is called Sauville (or Saubure, from the Japanese Sovyuuru) and its capital Saubrème. At the prestigious St. Marguerite school in this part of interwar Europe, a Japanese student encounters a nominal fellow student who does not attend her classes, despite being frighteningly intelligent. She prefers to sit on the checkered floor in a verdant indoor garden at the top of a very tall library building, reading several books at once and pretending to smoke a pipe, which for self-censorship reasons is empty on account of the character’s age. An eccentric inspector with the national police sometimes consults the solitary reader, whose origins lie in a still smaller kingdom, lost to history.
Ruritanian mystery. The actual mystery plots are on a typical young-adult level, i.e. poor, and this includes most of the ultimate revelations, with the possible exception of the identity of the great alchemist. The cute elements are on a tolerable level, more reminiscent of the clowning moments in Rurouni Kenshin (1996) than of typically misogynist moeblob fare. The Gothic elements are decent, and do indeed fall into much of the same silliness found in a mediocre Gothic novel, such as the sudden appearance of inexplicable identical twins with a flare for the dramatic, to dodge the Todorovian marvelous. I appreciate the alternate history, although there is really no explanation for the major large-scale deviation being 14 years early.
References here: Violet Evergarden (2018).