Aoi is a high schooler living in Kyoto, desperately wanting to return to Tokyo for love issues and almost willing to sell some antiques of her deceased grandfather. So she visits an antique shop for an appraisal, where she meets Holmes of Kyoto who offers her a job at the shop instead of selling the heirlooms without permission from her parents. What follows is a slice-of-life story of a high schooler living in Kyoto and getting involved with antique and how said antique is used to encode messages to various people, interspersed with a bit of of romance (of somewhat questionable age difference to be honest).
Personally I liked the slice-of-life, the travel catalogue to Kyoto and the insights into Japanese culture and some of its antiques. The romance was kind of simple, relatively wholesome, but not particularly dominate to the story. Still, the characters felt a bit bland and trope heavy. There was also not much of a mystery beyond the powers of observation and interpreting hidden messages behind various symbolism.
So if you want to read it for the mystery, well developed characters or plot driven story this book is probably not for you. If you want a slice-of-life story set in modern Kyoto with a some deeper lore on Japanese art (physical and literature) then you probably will enjoy it. For me it was a good somewhat quick entertaining read, but I certainly understand some of the lower ratings.