This page may contain spoilers related to the Kuroshitsuji series, including information from chapters not yet released in tankōbon format. Read at your own risk!
Jeremy is a relatively aged man with neatly trimmed, slicked-back dark hair. He has copper eyes, a narrow jaw-line and a distinctive nose. He attires in a clean, elegant black coat and a pair of dark trousers; additionally, he wears white gloves.
Though mysterious, Jeremy is an astute and extraordinarily shrewd individual, who exhibits acute mental discernment, which allows him to understand and discriminate between relations; for instance, he was able to accurately identify Karl Woodley due to the rare rings he possessed alone. He is very intelligent and well-versed in many different fields of study.
Furthermore, Jeremy demonstrates a keen enthusiasm for investigation and gathering knowledge, harboring hope that such activities would "relieve [his] tedium." He has stated that observing human beings is a hobby of his, as he can learn of a person's occupation and other crucial details simply from examining their clothing and habits.
Phantomhive Manor Murders Arc
Jeremy loudly knocks on the back door of the kitchen of the Phantomhive Manor. The Phantomhive servants, excluding Sebastian Michaelis, then capture and present him to Ciel Phantomhive and his guests. Ciel recognizes Jeremy, introducing him as Vicar Jeremy Rathbone to the rest. Karl Woodley insists that Jeremy must be the murderer as he should have no alibi, and Jeremy says that his reasoning is flawed. Karl is shocked when Jeremy correctly identifies him, but Jeremy proclaims that it is obvious who Karl is due to his rare rings. He, then, asks Baldroy to open his bag, which contains Sebastian's owl. Ciel reads the letter attached to its claw, and states that Sebastian has apparently anticipated his death and sent for Jeremy.
Grimsby Keane demands further evidence of Jeremy's innocence, and Jeremy has Finnian uncover a ticket for a play tucked in his coat pocket. Jeremy explains that he was watching The Lady of the Lake at the Lyceum Theatre—thus, he was not present when the murders occurred—and Irene Diaz confirms the validity of the showtime. Jeremy, then, insightfully concludes that Arthur Conan Doyle is a writer judging by his looks and habits, and explains that observing human beings is his hobby.
Shortly after, they free Jeremy from his ropes. They chronicle the perplexing string of murders for him. Jeremy, subsequently, petitions to see the bodies for himself and tells them to move each body to a separate room so that their individual scents would not interfere with one another. He also requests to change out of his rain-soaked clothes, and borrows some of Sebastian's. After the bodies are moved accordingly, Jeremy tells them to show him the bodies in the order that they were murdered.
Ciel, Arthur, and Charles Grey follow Jeremy along his investigation. While scrutinizing Georg von Siemens' corpse, Jeremy identifies that his only external trauma is the wound on his chest caused by a single stab with a sharp-edged blade. He deduces that Georg was a violent drinker because his expensive pocket watch has numerous scratches, hence indicating Georg's crude, drunk nature. He, also, perceives a strong scent of alcohol and a faint smell of the sea. He uses Arthur's handkerchief to dig into Georg's mouth; afterward, he sniffs it experimentally and returns it to a repulsed Arthur.
Next, Jeremy goes to Patrick Phelps, and inspects his peculiar neck wound. They begin to head to Ciel's room, where Patrick was murdered; however, Jeremy lags behind, presumably due to his advanced age, which snags Grey's then Ciel's attention. Jeremy apologizes, and they enter Ciel's room where Jeremy conducts his examination. He soon affirms that there are, indeed, more than one murderer involved, and adds that it will be more difficult to catch Patrick's murderer than Georg's. He discloses that in order to catch Patrick's murderer, they must wait until nightfall and rely on Ciel's cooperation.
In due course, Jeremy studies Sebastian's corpse, and comments that he was killed rather simply. When they are about to head back, Jeremy tells them that he must oversee some preparations for that night.
Later, Jeremy proceeds to the kitchen and discovers that the Phantomhive servants are out of food provisions. He, then, suggests using herbs to stifle hunger and reduce consumption, and turn the soy beans they have in excess into soy meat, which should produce enough hamburg steaks to feed thirty people, much to the awe of the servants. Mey-Rin, then, mentions a bottle with a deep red liquid that Irene possesses, which intrigues Jeremy, who then claims that he can guess what the liquid is, though he refuses to tell them until that night. Instead, he opts to help them with dinner.
After the group finish eating dinner, Lau presses for the truth behind the incidents, but Jeremy advises them to not be hasty. Jeremy, then, asks for Ciel to remove his clothes, much to the Ciel's dismay.
Jeremy, Arthur and Grey sit together, while a bare Ciel is constrained to keep quiet and stay still and patient, as instructed by Jeremy, who is positive that the Patrick's killer will emerge if Ciel does as told. Jeremy times Patrick's killer's movements carefully, and at the precise moment, launches their counterattack. Ran-Mao, dressed in Ciel's clothing to attract the killer with his scent, lunges from her hidden position, and Grey is about to stab Patrick's killer, but Jeremy stops him, saying that the killer is an important witness.
Subsequently, to the rest of the group, Jeremy unveils Patrick's killer: a Black Mamba snake from Africa, trained to attack when it detects Ciel's scent—this shifts the attention to Karl specializes in African trade. When Karl argues that he has an alibi, Jeremy remarks that an alibi may not be worth much; as inferred by Jeremy, Georg was in cahoots with someone and had initially faked his death with a substance called Tetrodotoxin—if refined, he elaborates, one can achieve a state of apparent death like the character Juliet in Romeo and Juliet. He adds on that the faint scent of sea he distinguished earlier was, in fact, Tetrodotoxin, also a poison puffer fish and octopuses carry. Jeremy, then, continues delving into details: Georg, at first, was encouraged by another individual to feign his death and tossed the ampule of poison in the fire, but then, he was actually killed later by the said individual; the murderer, then, attempted to destroy the evidence, but Sebastian was already collecting the ashes by the fire, so he murdered the butler as well, recovered the evidence and returned to his room. Grey demands for the ampule of poison as proof, and Ciel suggests that it may be found in Karl's hearth. Grimsby searches the hearth and finds glass shards, which Jeremy reassembles into the ampule.
Ciel, then, points out Karl's possible motive: to protect his diamond industry, which could have suffered a huge loss had Ciel and another major company cooperated with leading technology at their fingertips; thus, Karl tried to eliminate Ciel. After Grey arrests Karl and takes him away, Finnian asks for an explanation of Irene's bottle of deep red liquid. Jeremy, then, enlightens them: the liquid contains an extract of red perilla, which has an anti-aging effect. He adds that it can also assist one to recover from fatigue; he proposes that they toast with it to celebrate the closing of the case.
The next morning, Jeremy knocks on the window to Arthur's carriage to get his attention. In French, he thanks Arthur for taking care of Ciel.  Arthur, later, rushes back to the Phantomhive Manor, and declares that Jeremy is Sebastian. Arthur backs up his claim by saying that both Jeremy and Sebastian were "too perfect" to be different people. While stating that they have gravely underestimated Arthur, Jeremy removes his disguise, revealing that he is, in fact, Sebastian.
- "There are as many means to an end as there are stars in the sky. However, the fact remains that there exists one truth."
- (To Arthur Conan Doyle) It's a simple feat to tell a person's occupation and such from their clothing and habits. First, you have a large writer's callus on the middle finger of your right hand. And its shape differs from that of those who draw or paint. In other words, it goes to show just how much you write. Next, that blue smudge on your sleeve. This can happen when laundering fabric to which colored ink has adhered. And lastly, you have made a habit of noting on your cuffs with pencil story ideas as they strike you so you do not forget. Pearl, India, secret room, sign. Only a writer would do something like that, hmm?"
- (Regarding the Phantomhive Manor) "It seems this manor is bursting with the fragrance of a heady mystery that will relieve my tedium."
- According to the official Kuroshitsuji character popularity poll, Jeremy is the forty-third most popular character in the series, with five votes. He shares this spot with Fred Abberline and Eric Slingby, who also received five votes.
- Jeremy Rathbone's name and character are based on the Sherlock Holmes' actors Jeremy Brett and Basil Rathbone.
- Jeremy has deduced that Georg von Siemens was a heavy drinker by the scratches on the back of Georg's watch. In the original Sherlock Holmes novel The Sign of the Four by Sir Arthur Conan Doyle, the title character uses the same technique.