Narumi is a villain in the manga Riki-Oh. He is one of the Four Emperors and the leader of the north cell block.
Narumi is first seen after the guards restrain Riki-Oh for killing Bando and Iwata. Narumi informs Riki-Oh that he'll take care of him after Riki Oh confronts Administrator Sugiyama. After one of the prisoners attempts to kill another prisoner, Narumi mortally wounds the attacking prisoner with a saw. Sugiyama saw this and devised and plan to lure Riki-Oh into fighting Narumi and gives him a knife. As Riki-Oh battles Narumi, Narumi throws glass from the knife into Riki-Oh's eyes, blinding him, then proceeds to sever a tendon in his arm. Riki Oh eventually gains the upper hand after regaining his sight and tying the tendons in his injured arm. Narumi, accepting defeat, commits seppku and Riki-Oh rushes to him, but then Narumi attempts strangle Riki-Oh with his intestines. This fails and Riki-Oh ultimately kills Narumi with a blow to the head.
- Narumi is known as Oscar in The Story of Ricky.
- In the OVA, his fate is less graphic than the manga and live-action film; his eye does not pop out, nor does he commit seppuku to strangle Riki-Oh with his intestines.
- Asa greatly admired Narumi; in the live-action film, Narumi/Oscar is Asa/Alan's godfather.