Jumbo, as his name would suggest, is an extremely large man, who seems to have a slight hunch. He is bald and has yellow eyes, as well as red tattoos of fire on the back of his head, on his shoulders and on his forearms. He also has multiple piercings in each ear, wearing thick hoop earrings similar to Joker's. Jumbo wears baggy yellowish-brown pants with elastic bandages wrapped around his shins and black ankle boots; he is typically shirtless, save for a medallion he wears strapped across his chest. In the past, his appearance was similar to the way he is now, with the notable exception of the tattoos and piercings.
Jumbo encompasses the role of the voice of reason among the circus members. He is very calm and level-headed and is not prone to giving in to his emotions.
Additionally, Jumbo is extremely kind and generous, once stopping his work to help Dagger play with the other children in the past. Even though he is willing to kill people in order to carry out his orders, he is genuinely unhappy about having to do so; after attacking Finnian, he had apologized to him, thinking he was dead.
In 1879, 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. After Doll ran off, Peter angrily questioned why he wasn't allowed to speak, to which Jumbo replied that it was hard to break the truth to her whilst seeing her smile like that. Jumbo, Joker, Beast, Dagger, Peter, and Wendy 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 and an exhausted but happy Jumbo smiled along with her. 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, to the dismay of the others.
As thieves, they were mostly unsuccessful, and they barely managed to survive. However, he and the others were later picked up by Baron Kelvin and came to live in his manor. There, Jumbo busied himself with manual labor, such as chopping up wood. He, however, took the time to offer Dagger a ride on his back and to help him play with other children. When the others decided to start a circus, Jumbo became the fire eater.
At a circus show that Ciel Phantomhive and Sebastian Michaelis attend, Jumbo is presented by Joker as the fire-eating man, and he performs befittingly. Later, Joker introduces Ciel and Sebastian, new second-tier members, to Jumbo and the rest of the group.
Eventually, Snake informs Jumbo, Joker, Dagger, and Peter that Ciel and Sebastian were in their tents. Jumbo cautions that they cannot act yet, in case Ciel and Sebastian are associated with Scotland Yard. They agree that Joker should speak with Father first.
The following day, when they learn that Ciel and Sebastian have left the circus, Peter angrily strikes Doll. Jumbo stops him from continuing to hit her, stating that it is not something they should be doing right now. He then declares that it would be dangerous to continue to stay where they are. The first-string circus members reach a consensus that they will enact Father's plan the next night, out of fear of delaying and hence allowing the opportunity for Ciel, their special target, to leave London.
The next evening, Jumbo and the other first-string members arrive at Phantomhive Manor. In the interest of getting through the manor quickly, they decide to split up. Jumbo heads across the yard, where he encounters Finnian who just woke up. He attacks Finnian, and apologizes, saying that it cannot be helped. However, Finnian survives the assault and bashes Jumbo's head into the manor's wall. Before Finnian delivers the finishing blow, Jumbo yells for the other circus members to escape while they can.
- "Father said that this target was special. We must do something about it while we are here. Any failure on our part will incur his wrath."