Ryo Yuki is Seleção No. 10, one of twelve participants in Mr. Outside's game to save Japan. He allies with Seleção No. 1, Daiju Mononobe, to orchestrate the Careless Monday missile attacks on Japan, firing ten missiles that cause widespread panic but no fatalities; this event serves as the catalyst for the series' plot. Yuki's background and origins are not disclosed. As a Seleção, he possesses a specialized phone connected to the support system Juiz, providing access to 10 billion yen to fund his plans. His primary known action is coordinating Careless Monday with Mononobe. Later, he participates in a second plot to fire sixty additional missiles at Japan, a plan thwarted by Akira Takizawa and the Eden group. Following this second failure, Yuki destroys his Seleção phone, severing his connection to Juiz and Mr. Outside's resources, eliminating him from the game. His elimination occurs off-screen, and his subsequent whereabouts or activities are not detailed. His role centers on his alliance with Mononobe and their shared strategy of using large-scale destruction to instigate societal change. He undergoes no significant development, remaining an ancillary antagonist whose actions drive conflict involving other Seleção and Akira Takizawa.