Originating in the manga *Osomatsu-kun* as a recurring character conceived by Kenichiro Takai under Fujio Akatsuka, Dayon was devised to expand the supporting cast. His name stems from his distinctive verbal tic, ending sentences with "dayōn" or "yon".

Physically, Dayon possesses an abnormally wide mouth stretching his face into unrealistic proportions, along with facial stubble and a long curly mustache. His head narrows at the top and widens dramatically toward the prominent mouth. He typically wears a khaki-colored suit, initially paired with geta sandals, shifting to leather dress shoes in modern adaptations like *Osomatsu-san*.

Dayon exhibits a versatile yet enigmatic personality, officially described as an "unclear man whose identity cannot be easily understood." Often appearing easy-going, his traits shift depending on the role, ranging from neutral to antagonistic. His large mouth enables comedic gags involving gluttony—swallowing objects like 50 apples or even people—and utility, such as forming snowballs. Early *Osomatsu-kun* appearances also depict him enjoying haiku.

Across media, Dayon occupies minor roles, frequently appearing as policemen, shopkeepers, or background figures. His portrayal in *Osomatsu-san* shifts toward a cryptic "phantom" archetype, performing strange, unexplained actions without narrative focus. His relationships fluctuate: sometimes depicted as Dekapan's best friend and other times as one of three brothers (a pilot, ship captain, and truck driver) reunited after WWII separations. Occasional appearances include a wife sharing identical facial features, minus the mustache.

Beyond the *Osomatsu* franchise, Dayon appears in numerous Akatsuka works via the Star System, including *The Genius Bakabon*, *Extraordinary Ataro*, and *Nyarome's World Expo Surprise Surprise Surprise Guide*, consistently in minor, background, or gag-oriented roles.

His face was modeled after Kiyoichi Tsunoda (brother of Jiro Tsunoda) imitating pushing his face against glass.