Again with the broken timeline/science. Everything else is amazing about this series but the writing is just not really well thought through at times.
Your really gonna tell me people knew about swabbing for fingerprints during the time of Imperial China. Even if this is based during the later imperial times it would still be early 1900s at the latest. Which most of the things shown here weren't heavily practiced during the later imperial Era. The last two emperors of china before the communist revolution barely practiced long standing imperial traditions with Puyi basically throwing out most traditions due to the curcumstances of his reign. Its kind of what caused China to be unstable enough to go through multiple revolutions.
Should be marked as historical low fantasy at this rate.