Ishima is an elderly male staff member at the death office, a transitional administrative facility that determines final destinations for the deceased. His physical appearance reflects advanced age, consistent with his background.

Ishima died by suicide after experiencing financial ruin from a failed business venture, which resulted in overwhelming debt. His subsequent abandonment by family contributed to this decision. These circumstances directly connect to his presence within the death office.

He performs duties alongside other staff members sharing similar death circumstances. Specific responsibilities and interactions with the deceased remain undocumented in available sources.

Ishima appears in the live-action television drama adaptation as part of the office workforce. He also features in the original net animation special "Ashita no Watashi" (Tomorrow's Me), which adapts a source material story. No significant character development, expanded backstory, or role changes across adaptations are documented. Information regarding appearances in spin-offs, later seasons, or expanded universe materials is unavailable.