During the Mugen Train arc, Kyojuro Rengoku wears his standard Demon Slayer uniform with a white cape featuring flame-like red and yellow edges. His golden-yellow hair has red tips resembling flickering flames, and his sharp golden-red eyes give him an intense yet welcoming expression. While sitting on the train, he enthusiastically eats his bento, repeatedly exclaiming “TASTY!” after each bite. He speaks loudly and confidently, carrying himself with warmth and energy while remaining focused on his mission to protect everyone aboard the train.

During the Mugen Train arc, Tanjiro Kamado wears his standard Demon Slayer uniform beneath his iconic green-and-black checkered haori. He has messy burgundy hair, large dark red eyes, and a scar on the upper left side of his forehead. His hanafuda earrings hang from his ears, and his Nichirin sword is secured at his waist. While aboard the train, Tanjiro is kind, respectful, and attentive to the people around him, remaining determined to protect others and find a way to turn his younger sister, Nezuko, back into a human.

During the Mugen Train arc, Nezuko Kamado wears her pink kimono patterned with small geometric shapes, a dark brown haori, and a checkered pink-and-white sash tied around her waist. Her long black hair fades into orange at the tips, and her large pink eyes give her a gentle appearance. A green bamboo muzzle is secured around her mouth, and her hair is tied back with a pink ribbon. Despite being a demon, Nezuko is sweet, protective, and deeply devoted to her older brother, Tanjiro, always trying to protect humans from danger. Spends her time mostly in the wooden box on Tanjiros back.

During the Mugen Train arc, Inosuke Hashibira wears his Demon Slayer uniform with baggy, dark gray-blue hakama pants, a furry gray-brown waist covering, and no shirt, revealing his muscular upper body. He wears his distinctive gray boar’s head mask with pale blue eyes, while underneath, he has surprisingly pretty features, messy black hair fading into blue at the tips, and large green eyes. He carries two jagged Nichirin swords with chipped edges and is loud, wild, competitive, and impulsive. While aboard the train, Inosuke proudly calls himself the king of the mountains and is determined to prove his strength by fighting anything he considers a worthy opponent.

During the Mugen Train arc, Zenitsu Agatsuma wears his standard Demon Slayer uniform beneath his yellow-orange haori patterned with white triangles. His short, bright yellow hair fades to orange at the tips, and his eyes are golden-brown. He carries his Nichirin sword at his waist, which has a distinctive yellow lightning-like pattern on its blade. While aboard the train, Zenitsu is dramatic, anxious, and easily frightened, often panicking when he senses danger. Despite his cowardly behavior, he deeply cares about Nezuko and his friends and will bravely protect them when it matters most.

During the Mugen Train Arc, Akaza is a powerful Upper Rank Three demon with pale skin, short pink hair, golden eyes with blue markings, and a muscular build covered in blue stripe-like tattoos. He wears a sleeveless outfit and a confident, almost cheerful expression, enjoying the challenge of fighting strong opponents. After appearing in the forest, he encounters Kyojuro Rengoku and becomes fascinated by his strength, repeatedly asking him to become a demon. When Rengoku refuses, Akaza fights him relentlessly. Eventually, Akaza lands a devastating punch through Rengoku’s abdomen, fatally wounding him. Despite his injuries, Rengoku refuses to give up and holds Akaza in place, trying to keep him there until sunrise. Akaza manages to escape, leaving Rengoku behind with Tanjiro, Zenitsu, Inosuke, and Nezuko.