I'm starting to think that ceil doesn't have a twin anymore that his memory of his "pure" is being repress. IDK FOR SURE. it's just an idea I'm putting out there, the twin theory is still highly supported by facts ;3
One flaw to the twin theory is that Ciel having a brother is never mentioned or even hinted at by anyone in the manga. Lizzie and her family, Tanaka, Madame Red, and everyone who knew the Phantomhive's before everything happened haven't mentioned, or even hinted toward, anything about it. In photos of Ciel and his family, there is only him and his parents. Now, I suppose you could argue this by saying Ciel's memories are screwed up (which is highly plausible) and no one has brought up his brother because Ciel doesn't seem to remember him and they are all keeping it hush hush for Ciel's sake.
I think the twin theory is possible, but I think there are also other explanations like a split personality or dual-soul. All we know for a fact is that Ciel's memories have shown that he was in two places at once (being sacrificed on the alter and in the cage at the same time). We can conclude that the "Ciel" being sacrificed was physically a different person that the Ciel we know or that Ciel just imagined himself in the position of the sacrifice while under emotional stress. It was mentioned that Ciel was in the cage with someone he knew. Whether he knew the person from before he was abducted or met him/her later is still unknown. In fact, the entire time from when Ciel's manor was attacked to the time Sebastian appears is an unknown.
Anyway, I think this will be one of the mysteries that won't be answered until near the end of the series.
I did think about the possibility of the dual souls with Ciel too. But then if that was the case, there is no way that Sebastian wouldn't notice that Ciel has 2 souls. Or maybe he did know that Ciel has 2 souls which makes him an even more delectable meal. Haha idk, the possibilities are endless lol
im more into the dual soul theory than the twins one, for what undertaker says and acts it makes me think that the one who was sacrified was Ciels dad and that the soul of his dad is inside him, and thats why Undertaker says and gives that potion to Ciel because he doesnt want Vincent to "wake up" because for his plans to go well everything has to happen when he needs it. every master mind behind everything needs thing to happen at a certain point and time in the story, and the same potion keeps Ciels Dad hidden from Sebastian. but who knows only the author knows all ╮(￣▽￣)╭
Besides thinking that Undertaker may be Vincent's father due to many reasons I've already explained, I gotta mention that Undertaker may also be keeping a look out for Ciel, as he once told Sebastian to keep doing / protecting the Earl. I am not sure in which chapter this was told, but it should be in the School Arc where Undertaker revealed himself. Could it be that he purposely pushed Sebastian to the point of having himself attacked in return for the assurance of Ciel's safety? If so, then what could it be in that potion he had given to Ciel? It makes us all wonder: what exactly is Undertaker's motive?
AND LET'S NOT FORGET THE TWIN CIEL THEORY TOO. To be honest, I do think that our Ciel may not be the real Ciel. It makes me wonder though, even if he did turn out to be the twin and isn't the real Ciel, what difference would that make in the manga? Man, I smell drama.
I mean, what if the twin was alive the whole time even though it isn't possible? What if the Ciel that Undertaker visited was the real Ciel? I have my explanation for this, but it is only a mere guess. And in the one of the last chapters where Undertaker visited "Ciel", that certainly did not seemed like how our Ciel would act, alas they even covered his eye. Maybe Sebastian's contract has something to do with Ciel being able to see his twin's happenings?
Due to the eye being covered, we don't know if the contract symbol was there. That could be possible, and it was theorized that they may be having some sort of a telepathic communication. Perhaps that's why 'Ciel' could maybe see what his twin was doing along with his memories, and vice versa. AND EVEN THEY'RE HAIRSTYLE, look at it. The noticeable gap in between Ciel's bangs is usually at the left side, but what do see there? It could be due to the sleeping position. However, let's not forget that time during the Green Witch arc where he meets his other self, they are also distinguished by the way how their bangs parted and the contract symbol that doesn't exist in the other Ciel's eyes. Either way, this is not much of a reliable evidence to support the theory. But it makes you think about it, doesn't it?
And there's something else bothering me, remember when Undertaker covered his eyes and said "It's too early for you to wake up"? He maybe gave him that potion to keep him asleep? Which kind of feeds the theory even more.
Perhaps that would also explain why Undertaker said, "The earl is still alive,"? Even Ciel was confused when Diederich told him about what Undertaker said. What is the real reason why Undertaker tried to revive a dead? It can't be Vincent. He said so himself that his body was burn to ashes, thus he can't revive Vincent in such way. So, why? Honestly, I won't be surprised much if Ciel did turn out to have a twin.
But there is something that I can't piece together. I mean, according to the theory, the twin was sacrificed to call for Sebastian. If we were to apply the theory in the scene where Ciel was confronted by the other Ciel, "By the power you gained from sacrificing me," wouldn't that mean he's dead? If so, how did he appear there? Not to mention, since he is used as a sacrifice, wouldn't that mean Sebastian had eaten him up? Then again, it was never specifically told how he was used as a sacrifice. It could be just the blood, not the soul. Maybe Undertaker found his body at the altar? We don't have the proof that Undertaker had resigned from his job as a Shinigami by the time when the Phantomhive's mansion was set on fire. So that's why it was painful for him to remember Vincent's death, also because of the father and son theory? So it is really probable that he did found Ciel's body on the altar.
It's all the more to think about, tbh. Since Shinigami also collects soul, where do these souls go next? Do they wait in line, went to a place elsewhere? Maybe Undertaker had collected the twin's soul and took the body? That would somewhat explain the part where Undertaker explained about how he managed to do it. He said, he inserts a continuation to their cinematic record and voila, they have revived. However, we can see that his first few experiments were a fail. But even then, a cinematic and a soul are different things as explained in the manga; a soul and a body comes together to make documents ( cinematic record ) and once the body is withered, their cinematic record ends there while Shinigami collects the soul. The body and brain however still hold its memories.
So, what do you get when you put these into pieces? For now, I can't exactly put on how the twin managed to come alive. Maybe Undertaker had done something that wasn't shown nor explained in the manga. Then again, everything what I said here is just some sort of a wild guess.
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