Papa is the informal name used for Rikka Takanashi's late father in the series. He is a background figure who never appears in the present timeline, because he died two years before the story begins from a terminal illness. His death is one of the most important events in the series, as Rikka was very close to him and his loss led her to retreat into the chunibyo persona of the Wicked Eye as a way of coping with grief. Rikka's search for the Ethereal Horizon, a place she believes will allow her to reunite with her father, becomes the emotional core of her character arc and of her relationship with Yuta. His memory also affects Rikka's elder sister Touka, who wants Rikka to accept his death and move on, creating the main family conflict of the story. Papa is remembered as a warm and caring parent, and he appears only through Rikka's memories, flashbacks, and her longing to see him again. He has no notable abilities and no active role in the plot, but his presence defines Rikka's motivations and emotional development throughout the series.