Yuuki Kagurazaka, a Japanese otherworlder summoned to the Central World, appears eternally youthful despite being over forty years old. He maintains the physical form of a middle school student with black hair, dark brown eyes, and a height of 156 cm. His origin lies in Japan as a natural-born psychic; the death of his parents in a traffic accident caused by an overworked truck driver, followed by a court ruling that found the driver innocent, led him to recognize societal flaws and develop a desire to create a fairer world. He was summoned before acting on these plans. During the summoning, the near-death former Demon Lord Kagali—defeated by Leon Cromwell—attempted to curse Yuuki to steal his body for reincarnation. Yuuki awakened his Unique Skill "Creator" during the interdimensional transition, developing "Anti-Skill," a constitution that nullified Kagali's curse. He permitted Kagali to inhabit his body while promising to find her a new vessel, saving her life and forging a foundational alliance. For twenty years afterward, he operated in the eastern lands, collaborating with Demon Lord Clayman to build influence before moving west. Tutored alongside Hinata Sakaguchi by Shizue Izawa, Yuuki leveraged modern-world knowledge to restructure the adventurer society into the Free Guild, becoming its Grandmaster. He implemented systems like monster rankings and mission protocols, drastically reducing subjugation casualties and stimulating economic growth. Concurrently, he founded the underground organization Cerberus (reformed from the dark group "Echidna") and led the Moderate Harlequin Alliance, creating networks free from entities like Mariabell Rosso and her Council of the West. His ideology centers on achieving global peace and personal freedom through collective action, preferring political strategy over violence but resorting to manipulation when necessary. He values loyalty to allies like Kagali and the Moderate Harlequin members, though his methods often blur moral boundaries. Yuuki's relationship with Rimuru Tempest began cooperatively; he facilitated Rimuru's role as a teacher for Shizue's students and supported Jura Forest's stabilization. He expressed gratitude for shared manga and Rimuru's protection of children, even backing him against the Western Holy Church. As Rimuru's power grew, Yuuki shifted to viewing him as a strategic variable, culminating in his exposure as a mastermind during Tempest's founding festival. He attempted to frame the Rosso family for his schemes but was outmaneuvered by Granbell Rosso, forcing his flight. Fleeing to the Eastern Empire, Yuuki ascended to command its "Mixed Corps" and plotted a coup. This failed due to Kondo's intervention, leading to Rudra's mind-control over him. Later, he feigned subservience to the angelic entity Michael to study the Ultimate Skill "Mammon, King of Greed"—gained after stealing Mariabell's "Greed"—which allows energy drainage and memory manipulation via touch. He used this skill to break free, ally with Laplace, and rescue Kagali from Michael, but was ultimately betrayed and attacked by Jahil, leaving his fate unresolved. His abilities stem solely from "Creator" and "Anti-Skill," enabling him to nullify or absorb others' skills and craft new ones. He cannot use conventional magic, relying entirely on manipulating skills. His character portrayal diverges significantly between official media: the web novel depicts him as a primary antagonist treating allies as tools, while the light novel (basis for anime adaptations) frames him as a complex antihero motivated by idealism, emphasizing loyalty to comrades. Trivia notes his attachment to Japanese pop culture, particularly manga, and his catchphrase referencing a lunchtime TV show from his original world.