Jam Ojisan creates and cares for Anpanman, operating from his bread factory residence. He sports gray hair, fluffy eyebrows, a mustache, and rosy cheeks lighter than Anpanman's, usually clad in a white chef's uniform, apron, and blue-gray shoes. His vast knowledge, especially in baking and mechanics, allows him to invent devices like the Anpanman Mobile and repair mechanical beings, wisdom gained during extensive youthful travels chronicled in his many books.

He unintentionally birthed Anpanman when a "star of life" merged with an anpan he baked. He now bakes replacement heads for Anpanman whenever damage or hunger diminishes them, and extends his creations to other bread heroes like Melonpanna and Rollpanna; the origins of characters such as Currypanman and Shokupanman are ambiguously attributed to him across media. This theme responds to wartime starvation endured by franchise creator Takashi Yanase, emphasizing sustenance and compassion.

Jam Ojisan shares a fatherly bond with Anpanman, raising him since infancy and supporting his heroism. He maintains a familial, non-blood relationship with bakery assistant Batako, who repairs the heroes' capes. Their long partnership, potentially dating to Batako's infancy, forms a close-knit household. He also mentors younger characters like Melonpanna and Creampanda, offering guidance. Interactions with Rollpanna remain cautious due to her unstable dual-hearted nature, yet he repeatedly invites her to join the bakery community.

Within "Anpanman World," Jam Ojisan and Batako are considered fairies, as no humans exist. Early manga depicted him smoking a pipe, omitted later. His consistent role is as a benevolent inventor and knowledge source, central to sustaining Anpanman's heroism through bread production and mechanical support.