Mario runs "Marriott Lunch Market," a vintage clothing and select shop. This establishment serves as the essential location where Kakushi Gotō changes daily from his business attire into casual work clothes, helping him conceal his profession as a manga artist from his daughter. Kakushi notes the shop has relatively few customers.

Mario actively supports Kakushi's secret. He personally handles logistics for Kakushi's autograph sessions and provides a vehicle bearing his shop's logo for Kakushi's use, further enabling the deception. Mario humorously calls Kakushi "Clark Kent" due to the routine costume changes, reminiscent of the superhero's alter ego. An incident where Mario accidentally sold Kakushi's entire suit inadvertently led to the creation of a new fashion style.

Originally a minor character in the manga, Mario's role expanded significantly in the anime adaptation, including the theatrical version. The creator, recognizing the character's comedic and narrative potential through the animated portrayal, reintegrated him into pivotal later scenes. These scenes include Hime Gotō's birthday celebration and events depicted in the final episode, which aligns with the timeline covered by the theatrical edition. His involvement underscores his function as a consistent ally in Kakushi's ongoing deception.

His contributions remain centered on practical assistance tied to his shop and his collaborative dynamic with Kakushi.