Akiyama, often referred to as Ryuji Akiyama in production credits, was a prominent cast member of the Japanese variety program Pokémon Sunday. As a member of the comedy trio Robert, Akiyama performed alongside his regular partners Hiroshi Yamamoto and Hiroyuki Baba, forming a core comedic unit that drove many of the show's sketches and games. His role on the program was that of a performer and comedian, often serving as the physical centerpiece for many of the show's most memorable and absurdist segments.

Personality-wise, Akiyama presented a willing and adaptable presence, frequently subjecting himself to the show's often bizarre and physically demanding challenges. He displayed a high degree of commitment to his comedic roles, whether dressing in elaborate Pokémon costumes or enduring slapstick punishment. Akiyama's humor was often derived from his exaggerated reactions and deadpan delivery in the face of increasingly ridiculous situations created by his castmates.

One of Akiyama's most defining roles on Pokémon Sunday was his recurring character Yadon Akiyama, a personification of the Pokémon Slowpoke (known as Yadon in Japanese). This character was central to many sketches, often involving Akiyama wearing a distinctive Slowpoke costume. The Yadon Akiyama persona became so iconic that the program's final episode included a special farewell segment dedicated to retiring the character. His role extended beyond a single costume, however. In later episodes, Akiyama frequently appeared dressed as a wide variety of other Pokémon, including Yanappu, Victini, Maracacchi, Dotekkotsu, and Muggyo, as part of ongoing gags to find a new signature character. These segments involved him acting out Pokédex entries in humorous and often literal ways, such as trying to generate electricity while dressed as Muggyo or being subjected to wrestling moves as the muscular Dotekkotsu.

Akiyama's primary relationships on the show were with his fellow Robert members, Yamamoto and Baba. They often acted as both his partners in crime and the primary instigators of his misfortune, questioning his costume choices or putting his Pokémon-inspired abilities to the test. The trio worked seamlessly together, with Akiyama frequently playing the straight man or the willing victim to their antics. His motivations were rooted in entertainment; his primary goal was to generate laughs through his physical comedy, transformations, and the playful embodiment of the Pokémon world. While he did not have a narrative arc with emotional growth, his tenure saw a shift from the definitive Yadon Akiyama to an actor playing a revolving door of new Pokémon characters, demonstrating his versatility within the show's format.

Akiyama's notable abilities were almost entirely performative. He possessed a remarkable talent for physical comedy, a willingness to wear absurd and often uncomfortable-looking costumes, and the ability to commit fully to a sketch, whether that involved dancing, being hit with water, or having a sumo wrestler stand on his back. Beyond his costumed roles, he also participated in more straightforward gaming segments, such as attempting to catch the legendary Pokémon Ho-Oh in a live playthrough of Pokémon HeartGold, showcasing his persistence as a player. His efforts were a central pillar of the program's unique blend of Pokémon promotion and variety show comedy.