Eurynome is a demon appearing in the anime's second season, classified as a pig demon and bearing the moniker "King of Death." His signature ability, "Despair," inflicts profound hopelessness upon humans, draining their will to live or pursue happiness as a tangible force.

Originally contracted to Marukome Nobuki, a former bomb disposal expert in the Middle East, their bond formed from Marukome's deep-seated despair. This stemmed from a traumatic incident where villagers, including a child he cared for, ridiculed him after witnessing his severe hemorrhoidal condition during a mission. Eurynome sustains himself by feeding on and amplifying this human despair.

Eurynome possesses blue skin and a distinctive blond pompadour hairstyle, maintaining a chibi form with blue demonic traits. His personality reflects his despair-inducing power, often acting confrontationally towards other demons, such as when threatening Azazel with exposure of embarrassing writings.

A significant story arc occurs when Marukome is hospitalized for hemorrhoid treatment. Eurynome unleashes his despair ability on patients and staff within the ward, including Kōtarō Dōchin and doctor Reika Kikukawa, pushing them toward suicidal hopelessness. This draws the attention of Rinko Sakuma and other demons from Akutabe's agency. During the confrontation, Marukome challenges Sakuma to prove the world's worth, stipulating her death should she fail. Eurynome enforces this pact, though Sakuma's refusal to sacrifice herself ultimately nullifies the challenge.