Mario Nachi is a supporting character in the figure skating series Medalist. She is a former competitive skater who now works as a coach, running her own small training base in Nagoya called the Gravity Sakura-dori Figure Skating Club. Her only student at this club is Ryoka Miketa, and their coach-student relationship is central to her role in the story.

In terms of background, Mario was once ranked among Japan's top twelve skaters and held the designation of a Designated Skater from her early Novice B years through the start of her Junior career. She was particularly known for her high jumps and was capable of landing a Quadruple Salchow. She originally trained at Meijo Crown FSC under a coach named Akira Ryugu. However, she struggled to connect with the students she coached at that same club, which led her to leave and establish her own program.

Personality-wise, Mario has a fun, teasing, and exaggerated style of communication that is quite different from the traditional, reserved approach many coaches adopt. She is lively, wears multiple piercings, and projects a bold and confident exterior. Yet, this boldness tends to fade into bashfulness when she is around people she does not know well. Her unusual coaching personality meshed particularly well with Ryoka Miketa, in contrast to the friction she experienced with her earlier students.

Mario's primary motivation as a coach appears to be fostering Ryoka's growth as a skater in an environment that suits Ryoka's temperament. She brings her own competitive experience and technical knowledge, especially in jumps, to this role. Within the larger story, Mario functions as a mentor figure who operates outside the main coaching circle of the protagonist Inori Yuitsuka, but her presence highlights the different paths skaters and coaches can take in the competitive figure skating world. Her development is tied to her learning to apply her own difficult past experiences as a skater and coach to a more positive and effective partnership with Ryoka.