Ryutarou Oyama features in the Cardfight!! Vanguard franchise, prominently within the Shinemon Arc. As Dragon Empire Branch chief, he oversees branch operations but routinely delegates administrative tasks to his subordinate, Mamoru Anjou, choosing to prioritize cardfighting over managerial duties. His free-spirited nature drives him to seek enjoyment through battles against strong opponents, deliberately modulating his skill during matches to prolong excitement and ensure mutual satisfaction. This approach, paired with a gentle demeanor and formidable strength, commands deep respect from Mamoru and fellow Dragon Empire employees.

To evade work responsibilities and encounter intriguing fighters incognito, he adopts the cosplay persona "Vangarou." His distinct appearance includes extremely spiky gold hair, an orange t-shirt layered over a white undershirt, blue jean shorts, and a tooth necklace. In the Shinemon Arc, he employs a Narukami clan deck focused on Dragonic Vanquisher, supported by units like Thunderstorm Dragoon, Demonic Dragon Berserker, and Choubatsu, alongside triggers: Zephyr Kid (Front), Yellow Gem Carbuncle (Critical), Wyvern Guard, Guld (Draw), and Worm Toxin Eradicator, Seiobo (Heal). Documented Shinemon Arc outcomes include a victory against Tonori Fujinami, losses to Mark Whiting and Yuichirou Kanzaki, and undetermined results against Bear and Shinemon Nitta.

His broader activities encompass organizing events—such as a festival hosting a 3-on-1 match against Mamoru Anjou—and facilitating Dragon Empire quests to aid fighters like Chrono Shindou. He openly opposes victory-centric ideologies, explicitly rejecting Kanzaki’s "victory is everything" philosophy. During inter-branch conflicts, he advocates for Branch Chief meetings while maintaining his stance against win-at-all-costs mentalities amid challenges from fighters pursuing alternative resolutions.