Mami Futami is one of the twin idols from 765 Production, first appearing alongside her sister Ami Futami. Initially, both sisters performed together under Ami's name, their twin status a secret known only to 765 Production staff and Takane Shijou. Mami ties her hair to the left to distinguish herself from Ami, who ties hers to the right. As the older twin, Mami displays slightly more maturity and obedience compared to her sister, though both share energetic, hyperactive personalities, enjoy imitating others, and playing pranks. They respond obediently when corrected by the producer or staff.

Their family includes parents, with an occasionally overprotective mother prompting the twins to sometimes seek temporary refuge at the 765 Production office. Later, Mami grows her hair longer to establish a distinct identity separate from Ami, moving beyond their initial shared persona. This change reflects her desire to be recognized as an individual idol while maintaining her close bond with her sister.

In Shiny Festa, Mami participates in the music competition with Ami, Hibiki Ganaha, Yayoi Takatsuki, and Iori Minase. The twins aim to win while enjoying their time on the tropical island. Though performing as separate idols in this event, they continue to sing all their songs together as a pair. Mami's promotional profile for Shiny Festa describes her as the "Ultimate lovely queen," with her in-character quote expressing playful ambitions to "enslave the world" with her charm during the island adventure.

The Shiny Festa OVA episode bundled with the game features Mami in its storyline specific to that version, showcasing her involvement in the tropical island activities and music-focused narrative. Across various media, including games and spin-offs, Mami consistently exhibits her characteristic playful speech patterns, frequent use of onomatopoeia, and enthusiastic approach to idol activities, balanced by her underlying maturity as the older twin.