Peter (ピーター, Pītā) is a first-string member of the Noah's Ark Circus. As a flying trapeze artist, he conducts his performances alongside Wendy; together, they are deemed as a duo "in perfect sync."
Peter appears as a young boy with short, thick blond hair. As part of his circus act, he wears a small hat adorned with feathers, a ruffled collar, a vest, puffy shorts with stars on them, and tights, all of which representing shades of green. His makeup consists of three diamonds painted under his right eye. When going out, he dresses in a cape-like coat and black gloves, with moons and stars charms attached; the charms act as hidden retractable wires used for attacking enemies.
In the past, Peter wore ragged, shabby clothes. Despite this seeming to be several years ago, he does not appear any older now than he did then; his growth is abnormally stunted.
Peter is short-tempered and unmannerly; he is prone to violence, and often makes rude, sarcastic remarks. He harbors no qualms about killing other individuals, or even striking or threatening other members of the circus. Despite his tendency to anger easily, he is capable of making quick decisions, such as when he abandons attacking Finnian to take out a more serious threat. He is perceptive and keen, as demonstrated by his ability to swiftly deduce the reason for the Phantomhive's large gun collection.
Peter may bear some ill will toward Doll, as he frequently belittles her as someone much too childish. He may also not be very fond of Snake, as he has threatened to take Snake's life if he fails to perform well. However, he cares deeply about Wendy, as he is almost always by her side, and tends to her injured ankle. He also seems to respect Jumbo, as he listens to his advice, and is greatly distressed when Jumbo is killed.
Peter grew up in an alley in East End, referred to as a gutter, with the other first-string circus members, less Snake. Joker stated that they came together because they were each defective in a way. In Peter's and Wendy's case, they are trapped in children's bodies. For this reason, even though they seem to be the youngest of the circus members, they may actually be significantly older; this is implied when Peter reprimands Doll for being a child, despite appearing to be younger than her.
Ten years ago, Doll rushed up to Joker one day with a tooth in her hand. She gleefully exclaimed that it fell out, believing that she would later get a coin from the Tooth Fairy and promised them that she would buy them all bread afterwards. Peter began to retort that the Tooth Fairy didn't actually exist but was prevented from doing so by Jumbo. When he angrily questioned why he didn't allow him to speak, Jumbo replied that it was hard to break the truth to her whilst seeing her smile like that. Joker agreed, additionally musing that gap teeth are too cute to be legal. Beast commented that if Doll did not get her coin next morning, she would be extremely upset, to which Joker decided that he should attempt to earn something. Joker opposed Peter's idea of stealing, stating that he had a feeling it would be wrong to use stolen money "this time". In resignation, Peter frustratedly exclaimed that he hated kids but decided to come along with him, stating that if they all go, they might be able to earn something. Peter, Joker, Beast, Dagger, Wendy and Jumbo then proceeded to work on manual chores earnestly all night long in order to earn a single coin for Doll. They were relieved to see they made it on time as they placed it beside her whilst she was sleeping. The next morning, an oblivious Doll showed off her coin to them, stating how happy she was that they could eat bread with it. However, in the belief that the Tooth Fairy would give her more coins, Doll later attempted to take out more teeth that weren't wobbly, which Peter found troublesome
As thieves, they were unsuccessful, and they barely managed to survive. At some point, Baron Kelvin found them in the alley and adopted them. After living at his manor for some time, they decided to start a circus, and Peter and Wendy formed the trapeze act.
At a circus show that Ciel Phantomhive and Sebastian Michaelis attend, Peter and Wendy are presented by Joker as the duo that forms the flying trapeze act, and they perform fittingly. After the show, he and Wendy mock Sebastian for getting bitten by a tiger. Later, Joker introduces Ciel and Sebastian, new second-tier members, to Wendy and the rest of the group. Sometime after Ciel and Sebastian joined the circus, Peter is intended to put on another performance. However, when Wendy twists her ankle, Sebastian is called in as her replacement, and because Peter insists on staying with her and refuses to give him a hand, Sebastian is forced to do the performance with William T. Spears.
Later, Peter gathers with Joker and Jumbo and learns that Ciel and Sebastian invaded their tents, their motives obscure. He insults Snake and Doll, and asks if they should carry out the plan that night. In the end, he agrees with Joker about consulting Father first. The next day, he slaps Doll after learning that Ciel and Sebastian have left the circus. He is stopped by Jumbo, and eventually concedes that they should carry out the plan the next night without Joker.
That night, they go to Phantomhive Manor, where they split up in an attempt to accomplish their goal quickly. After a little while, Wendy and Peter hear Jumbo calling out to them, telling them to leave the mansion. When they run to his location, they discover that Finnian has already killed him. Angrily, they approach Finnian and engage in a brief battle. They decide to split him in half with a wire strung between the two of them, but Wendy is shot by an unseen sniper.
Peter abandons Finnian, recognizing that the sniper is the bigger threat. He approaches the rooftop, where the shots came from, and finds a large number of rifles. Mey-Rin manages to land a shot on his left arm, and he rushes to conceal himself. To his shock, he discovers that Mey-Rin is the sole sniper and that the extravagant number of rifles is simply to shorten reload time.
Then, Peter decides it is necessary to warn Beast and Dagger, and leaps to go to tell them. While he is flying through the air, Mey-Rin aims a rifle at him. Subsequently, he lies dead inside the Phantomhive manor, indicating that the shots were powerful enough to propel him through a window.
- (To Snake) "Which means we're outta tonight's show, but I'll do for you if'n you make a mess of things!"
- (About Mey-Rin) "It's like Jumbo said. We'll have to temporarily split up. But if I don't tell Dagger and the others... What the hell is with these random people? Random? It sure is weird. Even if they have a huge amount of rifles, how come they can fire so accurately, and with such speed? They are using these rifles as though they are handguns!?"
- According to the official Kuroshitsuji character popularity poll, Peter is the sixty-first most popular character in the series, with one vote. He shares this spot with Funtom Corporation's unicorn, Claude Faustus, Johann Agares, McMillan and Rian Stoker, who also received one vote.
- Peter may be based on Peter Pan. They share the same name, dress in the green, arrogant attitude, their partners' names are Wendy, and are both stuck as children.