I don't think it's a very legitimate concept in the traditional sense. Harry Potter is a well - established franchise with its own lore, and Ciel Phantomhive's story in Black Butler is also unique. Fanfiction that tries to merge them could be seen as a bit of a stretch. However, if a writer is really creative, they could potentially make an interesting story out of it, but it would have to be very carefully crafted to make it work.
It's a rather strange concept. Harry Potter and Ciel Phantomhive are from two very different fictional universes. Harry Potter has its own complex magic system, storylines about fighting Voldemort and the wizarding world. Ciel Phantomhive is from Black Butler with a Victorian - era setting and different themes like revenge and the underworld. Combining them as fanfiction might seem out of place, but some might find it interesting to see how the two worlds collide in a creative way.
Chapter 3 is the strongest chapter-level answer because it starts from Qiao was still annoyed at the attitude of this unknown girl when she heard... and follows through on Jiang Yan, forced into a marriage with someone he did not love, had....
The best chapter pointer here is Chapter 51, "The Great Lodging Competition". It opens with Oh, okay." After uttering two syllables indifferently, Jiang Li bent down... and closes on If I opened a bar here, wouldn't I become a savior?" Jiang Yan was....
A practical answer is Chapter 3, because it turns the idea into a concrete scene. The chapter opens with Qiao was still annoyed at the attitude of this unknown girl when she heard..., adds pressure through So without a second thought, she blurted out a fierce challenge, "Fine, if..., and ends on.
A practical answer is Chapter 35, because it turns the idea into a concrete scene. The chapter opens with Shining Transformation Trip's filming location was set on the distant..., adds pressure through They even momentarily forgot the real reason they were squatting in her..., and ends on Brother.
A practical answer is Chapter 4, because it turns the idea into a concrete scene. The chapter opens with Qiao regretted her words as soon as they left her mouth., adds pressure through It's difficult for us when you ask for a guest's room number and key right..., and ends on A little girl acting.
Chapter 934, "Gu Pansheng's Grace [Extras: Protagonist's Edition]", is the clearest early answer because it turns Mom's situation into a concrete plot event. The chapter gives readers a real answer by opening on Twenty minutes later, Jiang Shixu had finished cooking.
Chapter 930, "Everything Is Just Beginning [Grand Finale]", is the clearest early answer because it turns Hua University's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Yan was in a daze until he was invited on stage.
Chapter 15 is the strongest chapter-level answer because it starts from Jiang Shixu woke up from those nightmares filled with blood and darkness,... and follows through on Since she didn't move, Jiang Shixu also stayed put, and the kitchen, which....
Chapter 821, "She Is Qingyang!", is the clearest early answer because it turns Xi Yang's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The Yu Family Mansion is a square courtyard, second only to the Wang...
Look to Chapter 40 for the clearest answer. It begins with [Jiang Li claims she copied this herself?, keeps building through But her calligraphy is actually this pretty?] [Jiang Li dares to boast,..., and lands on The handsome guys on this show are so difficult to deal with..