Gorobei Katayama is introduced as a traveling street performer who has made a living since the end of the Great War by entertaining people in city streets. He is a veteran of that conflict, which is how he comes to know the legendary samurai Kambei Shimada by reputation even before they meet in person. Physically, Gorobei is a lean older man with brown skin, short white or gray hair, and a noticeable scar on the left side of his face, often seen wearing a turtleneck. His personality is marked by a sharp contrast between his easygoing demeanor and his fearsome skill in battle. He often makes light of serious or dangerous situations, greeting threats with a joking and theatrical attitude. However, once engaged in combat, he becomes ruthless and calculating, revealing the hardened heart of a veteran warrior who feels joy at the crossroads of life and death. A core part of his philosophy is the view that all the world is a stage and the people merely players, a perspective he embraces as an actor who plays his part well.

His primary motivation is a search for thrill and the enjoyment of testing his skills against mortal danger, making his living as an acrobat and performer who puts his life on the line for entertainment. When Kambei offers him the chance to fight as a true samurai again, he accepts readily, not out of desperation but for the love of the challenge and the confidence in his own abilities. In the story, Gorobei serves as a crucial early ally and becomes a trusted member of the seven samurai assembled to defend a village. He acts as a sharp contrast to the idealistic youth Katsushiro and the boisterous Kikuchiyo, providing a calm, experienced, and often witty presence. He is notably skilled at dodging blows and can perform incredible feats of reflexes, such as plucking arrows and darts from the air or deflecting bullets with his sword. A master of scheming and battlefield tactics, his ability to read his opponents and the flow of combat is top-notch. While he is proficient with many weapons, including daggers and a bow, his weapon of choice is a staff.

His key relationship is with Kambei Shimada, whom he respects and who comes to rely on him as a right-hand man. He develops a camaraderie with the other samurai, particularly serving as a foil to the more serious members with his lighthearted observations. He is also noted for his ability to see past Kambei's stoic exterior. In terms of development, Gorobei is a complete and accomplished samurai from the moment of his introduction; his arc is not one of growth, but of demonstration. His story is defined by his ultimate sacrifice. During a raid by the bandits on the village of Kanna, he is the first of the seven samurai to be killed. He meets his end while saving the rest of his comrades from gunfire, being caught in an explosion after cutting down one incoming shell. His death is a pivotal moment in the narrative, showcasing the ultimate price of war and cementing his legacy as a brave and selfless warrior.