Black and Red 'Black Butler' Fanfic: What are some interesting plot ideas?

One idea could be that Ciel has finally achieved his revenge, but now he finds himself lost without a purpose. He then discovers a new threat to the underworld that he feels compelled to fight against. This could involve new characters and a whole new set of mysteries.

One idea could be an OC who is a detective from another country coming to London to solve a series of mysterious murders that seem to be linked to the supernatural activities in the Black Butler world. This OC could cross paths with Sebastian and Ciel as they are also investigating the same case from their own motives.

One interesting plot could be Undertaker's past being explored in more detail. Maybe he had a relationship with one of the other main characters' ancestors that comes to light and affects the present story. For example, if he had a connection with Ciel's family long ago.

One idea could be that Sebastian's sneeze is a sign of a strange magic affecting him. For example, a spell has been cast on him that makes him have an uncontrollable sneezing fit whenever he gets near a certain magical object. This could lead to comical situations as he tries to hide his sneezes while serving Ciel.

One idea could be a fanfic where the kittens in Black Butler have special powers. For example, they can communicate with spirits and help Sebastian solve mysteries that are related to the supernatural world in the Black Butler universe. Another idea is a story about the kittens' origin, perhaps they were created by some ancient magic long forgotten in the series' lore. They could be key to unlocking a hidden power or secret within the Phantomhive manor.

A cool idea for a fanfic could be that the reincarnation is not just of a human, but of a demon as well. A demon from a different realm is reincarnated into the Black Butler world and has to adapt to the rules and power dynamics here. This could lead to some really unique interactions with Sebastian and the other demons in the series.

You could write a fanfic where the Black Butler characters react to different art forms. Suppose they visit an art museum in a modern setting. Sebastian, with his refined taste, would have in - depth critiques of the paintings and sculptures, while Ciel might be more drawn to the darker or more mysterious artworks. Or they could react to a live theater performance, with Ciel being amazed at the actors' skills and Sebastian observing the behind - the - scenes details like the stagecraft and the actors' emotions.

Another plot could involve an OC who is a powerful magician from a foreign land. They come to England seeking a powerful artifact that Ciel also has his eyes on. This would lead to a series of battles and negotiations between the OC, Ciel, and Sebastian, with the OC having their own set of goals and motives that might not be entirely clear at first.

One idea could be exploring Pluto's past before he became a demon. Maybe he had a family or a purpose that was lost. Another could be a story where Pluto forms an unlikely friendship with one of the other characters in the Black Butler universe, like Mey - Rin. It could be interesting to see how their different natures interact.

A great plot could be that the triplets are given the task of protecting a special guest in the Black Butler universe. They have to deal with various threats while also trying to figure out the guest's true motives. They use their combined intelligence and physical abilities to keep the guest safe.