|Previous Occupation||Prefect of the Green Lion house of Weston College|
|Manga Debut||Volume 7, Chapter 32|
Diedrich is a German noble and long time friend of Vincent Phantomhive.
Diedrich is initially described by Vincent as impatient. He is shown to be a calm man, avoiding conversations if possible. He appears to quite rude, as he immediately left right after Baron Kelvin attempted a conversation with Vincent Phantomhive.
As a prefect of Green Lion, he follows the rules and will not hesitate to confront those who oppose it. He is also shown to accept defeat.
Noah's Ark CircusEdit
Vincent helped him in the Windsor case and wanted Diedrich's help in his latest case, but before Vincent could tell him what it was about, Baron Kelvin interrupted them. Diedrich is shown stating disapproval of Baron Kelvin, which led the latter to believe that only 'special people' could touch other 'special people'. Thus, it is possible that Diedrich could also be a minor reason as to why Baron Kelvin started to have a series of plastic surgeries in order to become more beautiful. Later, he and Vincent went to talk in private. 
Public School ArcEdit
As a young man, Diedrich attended Weston College and was the prefect of Green Lion with Alexis Leon Midford as his fag. He strongly disliked Sapphire Owl's prefect, Vincent Phantomhive, for his relaxed and unseemly behavior. After Vincent left all of the work for the school's annual cricket tournament to him, he confronted Vincent. The two decided to have a wager based on the results of the tournament, the terms being that the loser will grant one wish of the winner. Vincent won, and his request was that Diedrich become his fag, with no time limit. This established their life long affiliation. 
- He appears in the short story written by Yana Toboso for the Kuroshitsuji Comic Anthology called "With Father!" 
- He is nicknamed "Dee" by Vincent Phantomhive. 
- ↑ Kuroshitsuji manga, Chapter 32, page 6-8
- ↑ Kuroshitsuji manga, Chapter 75, page 14-26
- ↑ Kuroshitsuji short story, With Father!
- ↑ Kuroshitsuji manga, Chapter 75, page 27