Jacques-Rosé has long, black hair which he wears in a low ponytail under a baseball cap. He wears a black, short-sleeved shirt, a bomber jacket with a fur lining, and light-colored pants. He can generally be found with a confident smile on his face.
Jacques-Rosé is an energetic, friendly young man who is determined to be a hero. He has a strong sense of justice and throws himself into danger without a second thought for the sake of protecting the underdog.
He's also known to be a big eater.
Jacques-Rosé is dropped off at Chicago Union Station by his girlfriend, Rosetta. As he leaps out of her car, she makes sure he brings a wooden toy turtle with him and reminds him of his promise to take her to Dolce the next time he's in Chicago. As he boards, he chides the Young Conductor who rushes him, warning him that the Rail Tracer might eat him.
Later in the evening, he orders a large quantity of Chinese food at the bar of the dining car, convinced that it is all-you-can-eat. He compliments Jacuzzi Splot's face tattoo as Jacuzzi is trying to work up the courage to introduce himself to Isaac and Miria, and is part of the conversation that follows as they all eat together, including when Czeslaw joins the conversation.
When Nick, Vicky, and the Black Suits all burst into the dining car, Jacques-Rosé encourages the Black Suits and White Suits to put away their guns, offering to be their opponent instead for the sake of justice. The Black Suits, unimpressed, start shooting, and Vicky uses Jacques-Rosé's body as a shield. As Jacques-Rosé falls to the floor, Vicky thanks him for protecting him and notes that if he'd met a hero like Jacques-Rosé as a child, he may not have become a homicidal maniac. However, a Black Suit then shoots and kills Vicky. Jacques-Rosé remains on the floor.
Once Ladd, Turner, Czes Mary, Isaac, and Miria have all left the dining car, though, he sits up, the bullet having been stopped from reaching his heart by the turtle toy Rosetta gave him. Protected and rejuvenated by her love for him, he leaves the dining car to take down the villains on the train.
He comes across Isaac and Miria in a second-class hallway. Though they initially fear that he's the Rail Tracer, he reassures them and shows off the turtle toy that protected him, pointing out that Isaac's multiple sheriff's badges will protect Isaac in a similar way. He then warns them to stay put, offering to go ahead and keep an eye out for danger. In the process, he passes by Czes, who is frightened to see him alive and theorizes that he might be the Immortal.
When he progresses further into the train, he comes across the Rail Tracer picking off some Black Suits. The Rail Tracer demonstrates no interest in Jacques-Rosé, but Jacques-Rosé realizes that Isaac and Miria are headed this way and might be in danger. He backtracks in order to warn them and encounters Czeslaw. Relieved to see him alive, he reaches out his right hand to pat Czes on the head while inquiring about Mary. However, Czes stabs him, accusing him of being the Immortal trying to eat him. Jacques-Rosé falls to the floor, not comprehending.
However, the sound of Rosetta calling his name then wakens him in bed at home. Disoriented, he falls out of bed and tries to explain to Rosetta what has just happened; however, she warns him that if he doesn't hurry, he'll miss the Flying Pussyfoot.
They proceed to the station and Rosetta reminds him of his promise to take her to Dolce the next time he's in Chicago. Jacques-Rosé is troubled, still trying to sort out if he was just dreaming. But as he sees the Black Suits, the White Suits, and the Beriams get on board, he sits down and elects not to board the train.
As he and Rosetta turn to leave, they become embroiled in a conflict between a few members of the Russo Family and Nader Schasschule, who is working with a police escort. Jacques-Rosé leaps into action to protect Nader from the Russos, suspicious of their vendetta against Jacuzzi Splot. Rosetta, who has meanwhile tied up the Russos' guns, tries to convince him not to get involved for the sake of someone he only dreamed about, but he insists that the Jacuzzi that they're after is a real person, and he cannot allow evil to flourish. In the scuffle, he completely fails to notice when Rosetta stops one of the Russos from shooting him by teleporting their guns out of their hands. Finally Nader, who is reminded by his passionate defense of justice of his own childhood desire to be a hero for Sonja, shoots one of the Russos in protection of Jacques-Rosé and brings the conflict to an end. As Nader rejoins the police escort and departs, Jacques-Rosé waves him off and then suggests that he and Rosetta stop by Dolce now rather than the next time he's in Chicago.
1931 Another Junk Railroad Edit
Jacques-Rosé and Rosetta make a small cameo in Another Junk Railroad, when Fermet overhears Jacques-Rosé's decision not to get on board the Flying Pussyfoot despite having splurged on a second-class ticket. Fermet, who intends to stow away, then decides to hide out in what would have been Jacques-Rosé's cabin. He takes no further interest in the pair.
- Many of Jacques-Rosé's comments in the dining car, such as mistaking the Chinese food for all-you-can-eat, wind up in the mouths of Isaac and Miria in other iterations of the scene.
- Jacques-Rosé shares a last name with Esperanza and Maribel Boronial of the 1700s arc.
- According to a bonus comic at the end of the second volume, Jacques-Rosé's name was originally supposed to be Jack-Rosé (ジャックローゼ). However, because the character Jack also appears in this manga, Shijin resisted this idea and elected to make his name Jacques-Rosé instead.
- The conversation Fermet overhears about Jacques-Rosé's decision not to board does not match the conversation that appears in the manga.