Narumi is a secondary antagonist in the first part of the original video animation, serving as one of the Four Emperors who govern the prison and commanding the North cell block. Prior to his incarceration, he worked as an assassin, and his background likely involved organized crime, as suggested by his elaborate back tattoo depicting Kintarō wrestling a giant carp. He is almost always seen without a shirt, a visual choice that emphasizes his imposing build and his constant readiness for violence. His personality is defined by a love for sadistic cruelty and a complete disregard for fair combat; he regularly employs dirty tricks and underhanded tactics to harm his opponents. In the story, the warden orders Narumi to brutally beat an innocent prisoner named Imura nearly to death in order to provoke the protagonist Riki-Oh into intervening, giving Narumi a pretext to kill him. The plan fails when Riki-Oh instead kills Narumi during the confrontation. The closest person to Narumi within the prison is a young boy named Asa, who admires him, though this relationship does not temper his vicious nature. His most extreme and memorable ability is his willingness to self-harm in combat, as he once cuts open his own stomach and attempts to strangle his opponent with his own intestines, demonstrating both his desperation and his complete lack of conventional honor. He does not undergo any meaningful development or change; he remains a brutal and unrepentant enforcer of the prison hierarchy until his death.