Shigeru is a tall elderly man, with dark, slick back hair with many wrinkles on his face and a strange round indentation on his forehead. His outfit consist of a light jacket, pants and shoes.
Shigeru is a devoted member of the Time Vessel Association, which worships Master Tengen. To avoid Master Tengen from merging with a Star Plasma Vessel he was willing to hire an assassin to prevent that. He was also opposing Suguru Geto's views which led to his death.
When Toji Fushiguro brings the corpse of the Star Plasma Vessel, Shigero confirmed that the corpse was indeed Riko Amanai and offered Toji extra pay for his troubles. Shigero then explains about how Master Tengen spread Japanese Buddhism in the Nara Period and preached what would become the foundation of Jujutsu Sorcerer's. He then claims that the Time Vessel Association couldn't afford to allow an impure merger to take place, and they are ready to fall alongside the star if need be and takes the corpse elsewhere.
Later Suguru Geto comes before a new congregation made up of the remnants of the Star Religious Group and like minded people. Shigeru opposed Geto and when he stepped on the stage, he was brutally crushed to death.