Jijimon is an ancient, Mega-level Digimon who appears in Digimon Fusion as a wise elder and a guide to the main characters. His design reflects his age and wisdom, resembling a bearded old man with long, white hair, often seen carrying a distinctive cane. The name Jijimon itself is derived from the Japanese word for old man, a characteristic that defines his role and persona. As a species, Jijimon is described as having existed since the dawn of the Digital World, possessing a deep and comprehensive knowledge of its history and workings. While he holds incomparable power, he very rarely chooses to fight, preferring instead to use his intelligence to protect those who are weaker than him.

Within the story of Digimon Fusion, Jijimon primarily serves as an information source and a guiding figure for the Fusion Fighters. He resides in the Village of Smiles located in the Green Zone, an area under the protection of the series' protagonist, Mikey Kudo, and his partner Shoutmon. His role is to provide the team with crucial knowledge about the Digital World and the challenges they face. For instance, when a mysterious natural disaster causes giant plants to erupt from the ground in the Green Zone, it is Jijimon who runs up to explain the phenomenon, identifying it as a cyclical event while also noting its unusual, early, and large-scale occurrence. This established him immediately as a reliable source of exposition and wisdom for the young heroes.

Jijimon's role extends beyond simply offering advice from a safe location; he actively participates in the team's efforts when necessary. He becomes a direct ally of the Fusion Fighters, adding his ancient power to their cause. He is even used as a component in a DigiXros, a process where multiple Digimon combine their abilities. During a significant battle against the Death General Gravimon, Mikey performs a DigiXros that fuses Jijimon along with Cutemon, Dondokomon, Knightmon, PawnChessmons, Persiamon, and ChibiKamemon to form the composite Digimon known as G-Cutemon. This fusion is deployed to hold off the army of the primary enemy, demonstrating Jijimon's willingness to lend his power directly in combat to support his allies. On another occasion, the heroes embark on a mission specifically to rescue Jijimon after he is captured by a villain known as the Water Tiger. His knowledge of the local terrain and his unique ability to communicate with sea creatures ultimately prove vital in guiding the team through treacherous waters to escape the Water Tiger's traps. These events show his key relationships with the main human and Digimon characters, as they both protect him and rely on his unique skills.

Jijimon possesses a set of notable abilities that reflect his ancient nature. Although he seldom displays his true strength, his attacks are formidable. One of his signature techniques is Hang-On Death, a devastating ability that rapidly ages an opponent, causing their senses and strength to deteriorate and eventually leading to their destruction. Another physical attack is Gentle Punch, a powerful punch thrown from his left arm. He also utilizes his cane in combat with techniques like Claw of Doom, where he slashes enemies with the claws on the end of his staff, and Guard Stick or Guide Stick, which allows him to wave his cane over the ground to create a protective wall of earth. Beyond these combat skills, it is believed that Jijimon has the ability to summon humans from the human world to the Digital World during times of great crisis, further underscoring his role as a guardian who brings forth help when it is most needed.