Hakushaku Cain Series, Tousei Gensou Hakubutsushi Recommendations
Both are period pieces featuring a handsome and knowledgeable yet mysterious young man who becomes involved in unravelling a series of mysterious cases, including crimes. Both series also deal with the protagonists' backstories and complicated family histories.
They begin as dark, episodic historical mysteries with a young male main character. The main character has a strange backstory, issues with his father, and a faithful servant. Hakushaku Cain is set in late Victorian England, and Tousei Gensou Hakubutsushi is set in Japan at around the same time.