Sebastian is going to die
So, Yana has a big thing with foreshadowing, this is obvious because of the twin theory being so popular and then actually being canon. In this case there have been two major foreshadowings.
Sebastian “died” in Manor Murder Mystery. And
Sebastian literally almost died in Luxury Liners or at least showed us that death scythes could in fact kill him.
We all know that the series is supposed to end with Sebastian eating O!Ciel’s soul. Yana has said in one of her tweets that the ending for Black Butler was going to be far from a happy ending. It would be the opposite of what is originally planned out. O!Ciel dying is technically the “happy ending,” since everyone would be content and satisfied with it. The opposite of O!Ciel dying would probably be Sebastian dying rather than anyone else.
Also, if Sebastian died it would be the perfect place to end the series. The whole plot line is carried by this one character. Without Sebastian there would be nothing left of the series other than the aftermath, but still. No one would want that. No one would read it anymore if it continued on after. The fandom would just downfall from there. The series is called Black Butler.
Continuing on from what I had said about a death scythe being able to kill a demon. That’s probably how he is going to die. I was thinking about what Undertaker had said, about erasing Sebastian because he makes the earl miserable, and how he might actually succeed at that with the help of other grim reapers. Every reaper has it out for Sebastian and if they all were to attack him all at once…he dead.
There is a lot of evidence to prove this theory if you really begin to dig into it. The first chapter of the entire manga O!Ciel had said that he was hoping to see Sebastian weak or just losing. Baldroy has called Sebastian Superman many times but nonetheless that also means he has a kryponite. O!Ciel, probably because Sebastian has said multiple times that he would protect him no matter the cost.
As we go further into the series we see Sebastian’s character development appear much more dramatic and definitely the biggest character development. He not only expresses more emotion but he tends to act more human in a way. We can literally see he is under distress in the recent chapters now and it may just be Yana trying to get us attached to him even more. She created the perfect character to kill: the one who can’t. She makes him appear more human. He is a demon that does some pretty magical shit, he can’t do even a third of the things he does if he is a human. Yana makes him more human and more likeable then BOOM. She gets rid of him.
Just in general, everyone takes him for granted. The servants broke down and showed a great amount of weakness when he “died” in Murder. O!Ciel also showed some sort of weakness and panic when Sebastian was impaled in BoA. They all truly care for him more than they think they do. The problem is, it’ll be too late to show their appreciation for him. If he died, everyone would too.
A lot of people would assume that my favorite character is Sebastian because he is hot and shit, while that is true he hot, he is also the only character who I feel doesn’t always want things for their own benefits. For example when he fixed O!Ciel’s ring, it wouldn’t have benefited him of his soul, it literally does not effect him in the slightest. Just small things he does, and idk maybe it’s to make him appear more like the perfect butler and shit. Still, in chapter 145, he spoke out of turn and out of place to defend O!Ciel, no one but them and Blavat were in the carriage so it wouldn’t have mattered.
Another thing that has grabbed my attention and probably the attention of others is Sebastian the dog. During the flashbacks we see that Sebastian(I’m referring to the dog now) is mean to O!Ciel. He picks on him to prod at and is a little bitch to him. On the twins’ birthday, when O!Ciel find Sebastian in the closet, he removes his muzzle and says that he is no longer scared. Sebastian jumps up on O!Ciel and we all assume he would pick on him again. But he doesn’t, rather he shows him affection and steals him away for the dead body. ONLY TO DIE MOMENTS LATER!rip dog.
Maybe moments before Demon!Sebastian dies he kisses O!Ciel. Pleeeeease Yana, just once.
Movin along…This is just a theory. There was also another account that had made a post on this theory as well, so credit them for a couple of my points, I just forgot what account it was.