Yuki Shibayama is a first-year student at Nekoma High School and the backup libero for its volleyball team. Standing 163 cm tall with black hair parted in the middle and dark eyes, he is the shortest team member, possessing slightly thick eyebrows. He wears the libero uniform of a white jersey top and red shorts during matches; his hair is cut shorter post-timeskip. Shibayama exhibits a shy, gentle, and easily rattled personality, often appearing nervous or self-doubting. He struggles with confidence, particularly feeling overshadowed by Nekoma's starting libero, Morisuke Yaku. This triggers moments of anxiety, like excessively apologizing to Asahi Azumane during cleanup. Despite this, he possesses determination and gradually becomes more willing to socialize and assert himself. His development peaks during the Spring High Preliminary match against Nohebi Academy. After Yaku sustains an ankle injury, Shibayama enters the game. Immediately targeted as a perceived weak link by opponents, he initially fails a receive, fueling his self-doubt. Calming himself by reciting the team mantra at Kuroo's prompting, he recalls Yaku's words about the honor of being Nekoma's libero. Kenma limits his rotations to when Lev is in the back row due to Shibayama's inexperience. Resolving internally to prove his worth, Shibayama perfectly receives Suguru Daishō's serve at a critical set point, enabling Nekoma to tie the game. Later, he positions himself to cover Lev's blocking gap and successfully receives Kuguri's spike, directly leading to Nekoma's winning point. This performance earns Yaku's praise and marks a pivotal step in his confidence. In the "Land vs Air" OVA, featuring Nekoma's semifinal against Fukurōdani Academy, Shibayama appears primarily as a spectator. He observes and analyzes gameplay, noting how Kuroo's blocks strategically direct spikes toward Nekoma's back-row receivers to facilitate digs. He attempts to explain receive techniques to Lev, though Lev struggles to grasp the concepts. Shibayama frequently interacts with fellow first-years Sō Inuoka and Lev Haiba. He and Inuoka are often seen supporting the team together. He comforts Lev after a loss and later, during the Nohebi match, informs Lev he will support him from behind during rotations. Their successful teamwork in that match excites both players. He respects Yaku but feels intimidated by the pressure to match his skill level. Yaku's earlier advice about the libero role proves instrumental in Shibayama's pivotal receive against Nohebi. Following high school, Shibayama pursues professional volleyball. As of 2021, he plays as the libero for Tōkai Heavy Industries Esperanza, a Division 2 team. His skills are reflected in post-timeskip parameters, showing high ratings in serve reception and digs. His persistent concern during high school was improving through practice despite feeling unneeded.