Kei is one of the two central characters in the unorthodox hard surreal gag comedy, with his role defined in direct relation to the series' title and premise. The name Nar Doma itself is a portmanteau derived from combining the Japanese slang for narcissist and super masochist, with Kei representing the latter half of this equation. He is identified specifically as the diehard masochist, or domazo na, of the pair, and his extreme personality serves as a direct comedic counterbalance to the narcissistic protagonist, Hagito.

As a character, Kei is defined almost entirely by his masochistic tendencies, which are portrayed as his primary personality trait. The narrative describes him as a super, super, super masochistic individual, emphasizing that this quality is not merely an interest but a core, exaggerated aspect of his being that drives his interactions and reactions. Within the story's framework, he is part of a cast of highly idiosyncratic characters that surround Hagito. This group includes the unnaturally strong yet girlish Totono, the stylish office worker Saitou, and the extraordinarily negative Roku. Kei's role is to participate in the surreal gag comedy, with his masochism serving as a frequent source of humor, particularly in response to the actions and vanity of Hagito. His key relationship is with Hagito, as the pairing of a narcissist and a masochist forms the comedic core of the series.

Regarding specific background information, motivations beyond his inherent personality, development across the story, and a detailed list of notable abilities beyond his described disposition, no information is available. The available sources focus on establishing the series premise and character archetypes rather than providing a deep or evolving character arc for Kei. However, it is confirmed that the character has a designated voice actor who performs the role in the anime adaptation.