A genius quantum physicist, he is the chief overseer of the Gate Investigation Project, known as the "DOLL Project," at Logios. He also developed the Etheric Multi-Form Formation Engine "Journey to the Heavenly Path," which is central to the DOLL Project. Despite holding multiple titles within Logios, including commander of the DOLL Project, he prefers to be called Chief, reflecting his primary role as head of the DOLL lab.

He has blond hair, a well-groomed appearance, and is tall. However, he has significant scars from the Great Collapse, which is why he never removes his lab coat in public.

He is gentle, kind, and approachable, always smiling and often perceived as younger than he is. While Onogi handles the day-to-day operations of the team, Jeremiah holds a higher position. He is skilled at negotiation and adept at resolving stalemates by balancing various interests. He often mediates between the hardline Onogi and Manase, who focuses on the mental care of the DOLL unit.

He was the one who recognized the main character's high ether compatibility and personally hired them as an observer.