Mai, the middle sister, is a tomboy-ish 14-year-old girl. She has pink hair and usually wears sporty looking clothes. Mai is constantly reminded of her flat chest by her younger sister Mii which causes her to blow a fuse.

Early in the season she was acknowledged for having problems with constantly moving for which she got constantly depressed about to the point she refused to go to school. This was because she thought everyone hated her after making friends and then abandoning them. She understood the impact of their journeys on others, unlike Mii, but did not have the mental maturity, like Ai, to cope with it. Later in the series she makes friends with a classmate of hers, Konami. When it was time to leave, Konami helped convince Mai that she was wrong and in consolation Mai left a sketch portrait Konami they were to make for a class assignment for Konami as a departing gift stating that they'll remain friends forever, even if they never see each other again. While she waits for Mai's return, Konami passes away 2 years before the mansion is in a location where they could meet again. She still was hoping to see Mai again.

Later in the series Mai meets Konami's daughter and at first mistakes her for Konami, but quickly learns her name is Mai, the same as herself and named by her mother after her freind. The middle sister, Mai, discovers that Konami's daughter, Mai, has more in common with her than a name. She reselmbles what the younger sister Mai was like before meeting Konami and feels it's her duty to both Konami and her daughter to show her that way of thinking was wrong, just as had been done to her. Mai, the middle sister, ultimately gave up and failed at the time when she Konami had still been waiting for her even as she lay dying. This, compounded with Keith's words about the pain the girls bring to others, reawakening her depression in a much deeper manner. When she returns to visit Konami later and leaves, as a departing request, asks Konami to explain to her daughter what she felt so that she wouldn't follow the same path as the younger sister Mai.

Mai is, along with Mea, the maid, left when the mansion disappears into the future without them. It is during this time that Mai realizes that she cannot age and Ai explains the connection to the mansion and aging process.

(Source: Wikipedia)