Mai is the fourteen-year-old middle sister and a central figure in the narrative, often distinguished as the most emotionally grounded and sensible member of the trio. She has a distinct tomboyish appearance characterized by her short, boyish pink hair and a preference for sporty, practical clothing. Her young age places her in a difficult position where she is mature enough to fully understand the consequences of her family’s lifestyle but lacks the emotional coping mechanisms to handle it, a burden that her older sister Ai and younger sister Mii do not share to the same degree.

Her personality is heavily defined by the pain of constant farewells. The sisters live in a mysterious mansion that transports them through time and space, causing them to leave behind any friends they make in each new era. Mai struggles with this more than her siblings, leading her to become withdrawn and depressed to the point of refusing to attend school. She fears that by befriending people and then disappearing, she is causing them pain and being seen as a cruel person. This internal conflict forms her primary motivation: a deep desire for stable, lasting friendships and a normal life, which puts her at odds with the endless journey she is forced to undertake.

Her role in the story is that of the emotional center, whose personal growth drives much of the plot’s serious themes. A significant turning point is her friendship with a classmate named Konami. Unlike Mai’s previous fears, Konami helps her realize that the bonds she forms are meaningful and lasting, even if physically separated. When the time comes to depart, Mai leaves a sketch portrait as a gift, promising they will be friends forever. This relationship has a profound impact on Mai and later defines her key relationships. When the mansion returns to that era, Mai discovers that Konami has passed away, having waited for her return even on her deathbed. This tragedy, compounded by warnings from the character Keith about the suffering the sisters cause others, plunges Mai into a much deeper depression.

However, this painful experience fuels her most significant development. Mai encounters Konami's daughter, who is also named Mai. Seeing that the girl is withdrawn and bitter, just as she once was, Mai feels a sense of duty. She works to befriend the younger Mai and show her that her way of thinking is wrong, mirroring the very lesson Konami taught her. Through this act of guiding another, Mai demonstrates substantial character growth, evolving from a cynic who hated their journey to someone who accepts her reality and tries to use her painful experiences to help others.

Regarding her abilities, Mai is known for her significant physical strength and athletic prowess, fitting her tomboyish nature. She acts as an Action Girl, capable of taking on opponents in physical confrontations, and has a specialty in super speed or jumping, allowing for dynamic and agile movement. Unlike her sisters who possess powers like speaking to plants or healing others, Mai's primary asset is her combat capability and physical power.