Koma Jinguji, widely known by the nickname Jay, is one of the principal protagonists. His background is marked by a dramatic time displacement; he originally lived a century in the past in peace with his younger sister Tenna and his fellow butler Tsubasa Hayakawa until Tenna was consumed by a mysterious void, an event that sent Jay one hundred years into the future. He enrolls at Koyomi Academy under this new name and becomes the student council president, a position that allows him to investigate the circumstances of his past and search for his missing sister. Jay possesses a charismatic and highly confident personality, characterized by his intelligence and striking appearance. His elegant smile and sophisticated manner make him exceptionally popular among his peers, particularly the female students, and he is known for using his sharp tongue to flirt and tease others. Beneath this charming exterior lies an air of mystery and emotional distance, hinting at the burdens he carries. His primary motivation is the rescue of his sister and the pursuit of the truth behind the thousand-year history and fate of the Butlers. In the story, Jay serves as a central member of the academy's butler corps, a group of guardians who fight supernatural battles. Alongside his key ally Tsubasa Hayakawa, he travels through time to confront their archenemy, and their contrasting personalities form the core dynamic of the narrative. Jay is a highly skilled combatant with formidable supernatural abilities tied to his role as a time-affiliated Butler. Throughout his journey, he develops from a mysterious and displaced figure into someone who forges deep new bonds in the future while steadfastly working to unravel the secrets of his lost past.