We know, a devilish butler doesn't probably need a family. The same goes for Ciel, who is rich enough to pay servants. Even when it's like this, Ciel and Sebastian become a family. It's a distorted and grotesque version of a normal family, but the truth is that thanks to the contract he formed with Sebastian, Ciel can call his butler and have him doing anything, as long as he takes his blind fold off his eye and shout an order.

Even the contrary is true. Whenever Ciel needs it, Sebastian is there for him. The thing is, Ciel is still a kid. He found himself all alone with the family business to take care of, and with being the “Queen's Guard Dog”. It's only natural that sometimes, as every kid his age, he gets sick, or finds himself in trouble. That's when Sebastian, as a perfect butler of the Phantomhive, intervenes and fix everything back. As we said, it's a distorted version of a normal family, but still Ciel feels safe under Sebastian's guard. Even though they're only bound together by a contract!

As we said, their bond is strong, even though it depends on the contract. Yet, Sebastian is willing to do anything Ciel orders, even when it's apparently impossible. Let's not forget one important matter though; Sebastian is a demon. His nature is wicked by definition, and so even though he accomplishes every thing Ciel orders, there are moments where he takes the time to enjoy teasing Ciel.

For example, he puts intentionally Ciel in a dangerous situation, just to be sure to save him at the last moment. Like for example when Ciel and Sebastian were investigating about the Circus, during the Book of Circus series, and Ciel asked him to free the snakes after the first-stringers. Can you guess what Sebastian did? He freed the snakes, yes, but when Ciel was still hidden in a tent trying to get a clue about Joker and the others. And yet, Ciel found himself face to face with a snake, and was saved by Doll. Of course, when he asked Sebastian for explanation, he justified himself saying that he just followed Ciel's order to free the snakes after the first-stringers, and that he wouldn't have let him die, no matter what!

Sebastian is a demon; he is tricky, wicked and without a single trace of human sentimentalism. He is cold, and act without really understanding human pain and struggles. That's a coherence to be expected. Ciel is just a kid, and he is still 12-year-old. Looking at the picture, at a first glance we would expect a trembling little boy who doesn't actually know how to step forward after the big tragedy he had to face when he was only a little child, and since he was so lost, he just thought of forming a contract with a devil.

Well, that couldn't be more wrong. If Sebastian is evil by nature, Ciel is even nastier. Is it his past's fault? Probably it is. That doesn't change the fact that Ciel kills without regrets, following a logic that only he himself can understand. What's more, he is just as cold as Sebastian. There are moment when he shows a little bit of his emotions, but then again he hardens and goes on. Ciel is like an old cynical man hardened by the time, and yet he is still so young. So he is just the perfect match for Sebastian, who can maneuver Ciel the way he likes.

The third reason takes us directly to the fourth. The question is: in this master-servant relationship, who is the actual master? Let us explain this. Sebastian is bound to be loyal to Ciel, and accomplishes every single thing Ciel asks, even when it's all about Ciel's tantrum. Looking closely, though, it's impossible not to notice how much Ciel relies on Sebastian. Not just as a butler, of course, but even when it's about important decision. That's probably one of the few moments where Ciel shows a little his actual age. Sebastian doesn't have to struggle to deviate Ciel's mind, they just find themselves thinking the same.

Ciel asks for Sebastian's advice, and their thoughts strangely seem to correspond. When they don't, it's all up to Sebastian to give a little push that will make Ciel take the decision his butler wants him to take. So the truth is that even though the master is Ciel, the real master moving behind the scenes is Sebastian. He swore, by contract, to help Ciel finding the culprits who killed their parents, so he will put all his efforts to accomplish his duty and eat Ciel's soul in the end. It's a fair price to pay, letting Ciel think that he is the master!

We said that Ciel thinks to be the master, but the truth is that Sebastian leads him. Another undeniable truth is that Ciel couldn't do anything without Sebastian. It's not only about cooking food, or ironing the newspapers, or even dressing up. The thing is is that Ciel is a strategist, and very clever. When it comes to more practical stuff, though, he is totally clumsy. Let's not forget how he can't dance, or even peel two or three potatoes. That's why, Ciel needs Sebastian, because only Sebastian can reach the perfection that the Earl of the Phantomhive longs for.

Even the contrary is true. Sebastian needs Ciel. Even though, in the beginning, he simply formed a contract with Ciel like he would have done with anyone else, later on things change. Sebastian slowly grows curious about human nature, and Ciel is a perfect example that says how human being can be so corrupted, mean and yet so fragile. So as they pass their time together, Sebastian enjoys observing and studying human nature, not actually understanding it, but realizing how human can be more devilish than actual demons.

It's impossible to forget how, at the end of the Book of Circus series, Sebastian found himself surprised at Ciel's reaction. After realizing that the Circus members were sacrificing themselves to guarantee money to their little siblings in an orphanage that was destroyed years before, he burst into laughter. Sebastian thought, for a brief moment, that Ciel was crying, since it would have been the natural reaction of a normal person. Ciel managed to surprise Sebastian, making him think once again how ample and various human nature actually is. Ciel's laughter signed just how perfectly they fit each other.