Mari Katsuragi is a supporting character in The World God Only Knows. She is the wife of Keiichi Katsuragi, the biological mother of the protagonist Keima Katsuragi, and later the adoptive mother of Elucia de Lute Ima, known as Elsie, who comes to live with the family. Mari runs a café named Café Grandpa, which was originally a pottery workshop owned by her father-in-law, Denma Katsuragi.

In her everyday demeanor, Mari resembles a stereotypical mother from a shōjo manga: she is optimistic, cheerful, somewhat absent-minded, and deeply affectionate toward her family. She wears glasses and keeps her hair tied up, presenting a gentle and approachable appearance. However, when seriously angered she undergoes a dramatic transformation: she removes her glasses, lets her hair down, and her entire personality shifts to a stern, intimidating, and confrontational state. In this mode she is referred to as aniki, a term implying a tough older-sibling or gang-leader persona. Keima has claimed that she was once a member of a biker gang, and she has shown violent tendencies consistent with such a past. Despite this fearsome side, her underlying motivation remains the well-being of those she loves; she made the decision to raise Elsie as her own daughter while in this assertive state, fully accepting the demon girl into the family.

Mari’s role in the story is primarily that of a supportive parent and a source of comic relief. She owns the café that serves as a meeting place for several characters and provides a stable home environment, even as her son becomes involved in supernatural conquests. Her relationship with Keima is warm, though she often finds his obsessive gaming habits baffling. She treats Elsie with genuine maternal care, reinforcing the theme of family that runs throughout the series. While she does not participate in the main plot’s demon-hunting or goddess-awakening arcs, she inadvertently offers a contrast between the ordinary human world and the fantastic elements of the story.

Development for Mari is subtle. She is introduced as a typical loving mother, but later episodes reveal the depth of her personality, especially her hidden tough side and her past. The decision to adopt Elsie shows that her fierce persona can be channeled into protective and constructive family decisions. Her notable ability is not supernatural but rather her capacity to switch between extremes of personality, as well as the physical capability implied by her biker background. She also keeps her café running smoothly, demonstrating practical skills. Overall, Mari Katsuragi contributes to the series’ emotional grounding and humor, embodying a mother who is both soft and unexpectedly formidable.