Omusubiman is a wandering ronin character from the Anpanman franchise, depicted as a masterless samurai with a rice ball head who travels various lands to assist those in need. He adheres to bushido principles of justice, bravery, compassion, courtesy, honesty, honor, loyalty, and self-control. His appearance features a triangular rice ball head with dot eyes, rosy cheeks, and a pink nose. He wears brown traditional Japanese clothing, brown zori sandals, a greyish-blue cape, and a round straw hat.

He travels with a young disciple named Komusubiman, whom he mentors in samurai ways, forming a core narrative aspect of his role as teacher and protector. While his family or birthplace remain unspecified, he maintains a long-distance relationship with Butterko, involving gift exchanges and letters, an aspect infrequently highlighted in recent media.

Omusubiman appears in multiple Anpanman television episodes and films. His debut film, "Go! Anpanman: Omusubiman" (1990), is a spin-off where he serves as the sole protagonist, distinctively absent of Anpanman and Baikinman. This film adopts a jidaigeki aesthetic, focusing on his adventures in a narrative described as a fun, traditional painting-inspired short. He also features in other films including "Go! Anpanman: Tears of Planet Kirakira" (1989) and "Dinosaur Nossie's Big Adventure" (1993).

He wields umeboshi (pickled plums) to defeat adversaries, aligning with his rice ball theme. His filling remains officially unspecified, though umeboshi is heavily implied. He has a dedicated theme song, "Lunlun Omusubi Benevolence," originating from the musical "Fly! Anpanman; Anpanman and Omusubiman," which also establishes a narrative link to the space princess Lunlun Nanda.

His popularity led to spin-off books and shorts, though these remain loosely tied to the main franchise. In English-language adaptations, he is known as "Omusubi" or "Riceball-Head," though his role in dubbed content is often limited to background appearances.