I’m just gonna say this, please PLEASE read the novel , the anime is good and all but the novel IS SO MUCH BETTER!! A lot of stuff were skipped in the anime and it just feels like you’re doing the series wrong by only experiencing it from the anime. Sure the anime does convey the main plot and all but it does not show you how brilliant each side character is and how much effort and thought were put into them. The side characters are a really important part of the case files of jeweller Richard. Seigi and Richard really show their spark from theway they treat and deal with their clients, since the anime does not dig deep into the issues of the clients and the side characters.
To sum it up, if you want a deeper and a better experience read the light novels!