Jumbo is a first-string member of the Noah's Ark Circus, where he serves as the fire eater and fire breather, using his act to launch the troupe's performances with a dramatic blast of flames. His name, which means giant, is fitting for his most defining physical trait, as he is an extremely large and muscular man who often appears with a slight hunch. He is completely bald and has striking yellow eyes. His body is marked with red flame-shaped tattoos on the back of his head, his shoulders, and his forearms. He also has multiple piercings in each ear and typically wears baggy yellow pants with bandages wrapped around his shins, leaving his torso bare except for a medallion strapped across his chest.

Among the members of the circus, Jumbo acts as the voice of reason, possessing a calm, level-headed, and gentle nature. Unlike some of his more volatile companions, he is not prone to giving in to his emotions. Despite his intimidating size and the violent tasks he is sometimes forced to perform, he is fundamentally kind and generous. A clear example of this is when he willingly stopped his own work to give a younger Dagger a ride on his back, allowing the unhappy boy to join the other children in their games.

Jumbo's background is one of profound hardship. Like the other first-string performers, he grew up in the gutters of London's East End. Having been raised too harshly by his parents, he suffered from physical deformities that led to him being abandoned. Before being taken in by Baron Kelvin, he and the other children survived as thieves, though their efforts were mostly unsuccessful. This shared past of poverty and rejection forged incredibly strong bonds among the group, who came to view each other as a surrogate family. Jumbo was always a protective figure among them, once stopping Peter from crushing young Doll's belief in the Tooth Fairy, and then working through the night with the others to secretly place a coin under her pillow.

In the main storyline of the Book of Circus, Jumbo and his fellow performers travel to London, unaware that their patron, Baron Kelvin, is using their circus as a front to abduct children. When Ciel Phantomhive and his demon butler Sebastian Michaelis infiltrate the troupe undercover, Jumbo is present when they are introduced. After the pair's cover is blown, the circus members decide to launch an attack on the Phantomhive manor. Showing his loyalty to his orders, Jumbo participates in the assault, though he takes no pleasure in it. He confronts the gardener Finnian and, believing he has killed the young man, apologizes to him, explaining that his actions could not be helped. However, Finnian survives and turns the tables. In a contest of brute strength, Jumbo is overpowered and slammed against a brick wall. Before he dies, his final act is not one of rage but of selfless concern for his family; he shouts a desperate warning for the other circus members to flee the manor while they still can. His notable abilities include his exceptional physical strength, far beyond that of a normal man, and his skillful and dramatic control over fire as a performer.