Morisuke Yaku serves as the starting libero for Nekoma High School's volleyball team. Standing 165.2 cm tall with sandy blond hair and brown eyes, he wears Nekoma's distinct libero uniform during matches: a white jersey featuring red and black accents, red shorts, and knee pads. He harbors a notable insecurity about his height, a topic considered taboo by his teammates. Yaku initially joined Nekoma alongside Tetsurō Kuroo and Nobuyuki Kai. His relationship with Kuroo began poorly due to their middle school teams' rivalry, but the trio bonded over their shared ambition to win nationals. As a third-year, Yaku assumes a parental role, frequently mentoring first-years Lev Haiba and Yūki Shibayama. He conducts rigorous receiving drills for Lev, though their interactions often spark comedic conflicts stemming from Lev's tactless remarks about Yaku's height. On the court, Yaku is renowned for his exceptional defensive skills. His reflexes, speed, and game sense enable him to consistently dig powerful spikes, including those from Bokuto Kōtarō and Asahi Azumane. He excels at reading spikers' form and positioning himself preemptively, earning the moniker "Guardian of Nekoma's Defense." Bokuto acknowledges Yaku's receives "give him chills," while Karasuno's Nishinoya Yu respects his consistency and drive for self-improvement. During the Tokyo Prefectural Qualifiers, Yaku sustains an ankle injury against Nohebi Academy after leaping into the stands to save a ball. Benched, he supports replacement Shibayama and tearfully expresses pride when Nekoma secures the nationals berth. At nationals, he remains pivotal in matches against Kiyokawa and Sarukawa, notably devising strategies to protect an exhausted Kenma Kozume. In the "Land vs. Air" OVA, Yaku demonstrates top form during Nekoma's semifinal against Fukurōdani Academy. He repeatedly anticipates Bokuto's cross-shots and advises teammates on positioning for Bokuto's serves. He also interacts with Lev's sister, Alisa Haiba, who cheers from the sidelines. Following high school, Yaku pursues a professional volleyball career. As of 2021, he plays for Tigr Ekaterinburg in the Russian Volleyball Super League and represents the Japan National Team. Post-timeskip, his hair is slightly longer and combed back, and he favors stylish suits in casual settings.