Masao Sato is one of Shin-chan's friends. He is known to be a scaredy cat, and a bit of a cry baby. He is also a "clean freak" that borders on Obsessive Compulsive Disorder. Masao is usually the butt of the show's homosexual jokes since he often makes innocent comments that ironically sound homosexual in a different context. Masao is in love with Ai and gets furious whenever Shin rebuffs Ai's advances. His nickname is "Onigiri" due to his shaven head's resemblance to a rice ball. His friends use it as a term of endearment, while the people that bully him use it as a put-down.