I’m taking a moment to explain this since the manga, anime, and musicals are all in play in my posts. This isn’t unusual for me since there are many stories that I appreciate in multiple mediums, but Black Butler is one of the few that has a stage counterpart.
Due to personal preference, I generally will take the manga over the anime for canon. (The musicals vaguely fit in between the two) So I will be covering the manga’s costumes as well as the anime’s. For costumes, the manga tends to have greater detail (particularly with the cover art) but the anime has more angles, colour, etc. If I have a choice, I go with the anime and supplement as needed from the manga. This is, actually, pretty standard if you are familiar with my breakdowns.
However, whenever possible I do use the musical as canon references. Why? Because a professional costumer put the costumes together. They are going to be made in a way that is as true as possible to the source material while being practical for being on stage for 2+ hours with. I’ve also seen some behind the scenes footage which is good for noting things like hoop skirts, layers of costumes, etc.
But I don’t have access to a lot of high quality stills from the stage productions so the manga/anime will be my fallback on the costumes that overlap.
If I miss anything – please let me know, with a source photo for proof.