Mami Endo works part-time alongside Marika Kato at the retro Lamp House café, serving customers and performing waitressing duties. She remains entirely planet-bound, the only named character never involved in space activities or pirate operations.

Mami maintains a close friendship with Marika, offering civilian support. She possesses fashion design talent, notably modifying Marika's pirate uniform with a distinctive cape and other enhancements. Her creative skills extend to designing functional crew uniforms for the space yacht club's vessel, the Odette II, providing practical support through design. Her characterization consistently depicts a grounded, fashion-focused individual contributing to Marika's life via her café work and design abilities, separate from space piracy.