Mai Tachibana is one half of a teenage twin duo from Japan, journeying through South America alongside her sister Mami. They carry a stolen Ord artifact mirror, convinced it holds the key to ancient Ord civilization treasure. This belief drives them to seek out archaeologist Rayna Kazuki for help.

Physically, Mai presents a boyish look with short hair, embodying a tomboyish style she shares with Mami. Their mannerisms and overall design reinforce this youthful, androgynous appearance.

Mai leaps into action with daring resourcefulness when stakes are high. In the opening sequence, she and Mami evade pursuers by commandeering a train's engine handle and jumping from the moving train onto a truck below. This bold move underscores her significant risk tolerance and physical capability. Later, they demonstrate sufficient competence to engage adversaries in physical confrontations, holding their own in fights.

Their theft of the mirror from Rayna, leaving a note promising its return after finding the treasure, serves as the plot's primary catalyst. This act forces Rayna into pursuit, coinciding with antagonist Rieg Vader's own efforts to seize the artifact.

Personality-wise, Mai exhibits brashness and overconfidence. She boldly positions herself and Mami as indispensable to Rayna's success, explicitly stating Rayna is "helpless" without them—a claim portrayed as self-aggrandizing within the narrative, with Mami herself questioning its validity.

Mai's relationship with Rayna evolves from initial distrust and self-serving theft into a reluctant partnership. While Rayna adopts a protective role, Mai consistently maintains her independence and assertive presence throughout their interactions.