Mario is the proprietor of a tavern called Mario's Eden, which serves breakfast and dinner and provides lodging for travelers in the post-apocalyptic world of Cagaster of an Insect Cage. The main characters Kidou and Ilie live upstairs as residents and frequent guests. Mario's background is that of a caretaker and cook who takes great pride in the ability to cater to others. In terms of personality, Mario is initially stern but also loving and caring, with a strong, determined nature. They are willing to stand up for those in need and speak out against those who would do harm. Mario possesses a combination of feminine and masculine mannerisms, using the latter when necessary to drive a point home. Most people refer to Mario as a man, though some refer to the character as a woman, and Mario does not seem to care about which label is used. As a supporting figure, Mario serves as a stable, nurturing presence in the story, offering both practical food and emotional grounding to the main cast. Mario acts as a parent figure for Kidou, unafraid to confront him and put him in line when needed, and also shares information about Kidou's past, including how his adoptive father Lazarus taught him survival skills. Mario's motivations center on running the tavern, protecting those under their roof, and maintaining a sense of normalcy amid the insect-threatened world. There is no indication of special combat or supernatural abilities; Mario's notable skills are cooking, hospitality, and a resilient, caring disposition. The character shows minimal personal development over the series, functioning more as a consistent anchor and source of information and shelter for the protagonists. Key relationships include the close bond with Kidou, a more protective stance toward Ilie, and an indirect connection to Lazarus through Kidou's history.