Mai is a minor character in Battle Royale II: Requiem who first appeared as a brief figure in the news report that opens the original Battle Royale film. She was a student at Zentsuji Middle School whose class was selected for the Battle Royale program. Mai emerged as the sole survivor and winner of that year's Program, completing it in approximately two days. The traumatic experience of being forced to kill her classmates, however, left her psychologically damaged, and she was visibly driven insane by what she had endured.

In terms of personality, Mai is defined by the madness that resulted from her victory. When she was first shown on television hugging a bloodstained doll, she was smiling, but the expression was clearly that of someone who had lost their sanity rather than a sign of genuine happiness or relief. This crazed, sadistic smile remains her most consistent character trait. By the time of Battle Royale II: Requiem, she has become a member of the Wild Seven, a terrorist organization led by Shuya Nanahara that seeks to overthrow the totalitarian government responsible for the Battle Royale program. Her motivation appears to be tied directly to her past trauma, fighting against the system that forced her to murder her classmates and destroyed her mental state.

Mai's role in the story of Requiem is that of a supporting member of the Wild Seven operating out of their island fortress. Her presence serves as a visual reminder of the long-term psychological consequences of the Battle Royale program, showing that even winners do not escape unscathed. She is not a primary fighter in the organization's leadership but rather one of its more damaged and unstable soldiers. Her key relationship is with Shuya Nanahara as his follower within Wild Seven, though no detailed personal interactions between them are depicted. By far her most significant relationship is with her doll, the same bloodstained doll she clutched during her first appearance in the original film. She has kept this doll for at least four years following her own Battle Royale, suggesting a deep psychological attachment to it as a coping mechanism or a remnant of her trauma.

Mai's character undergoes minimal development, consistent with her status as a minor figure. She appears only twice in Requiem, first to display her characteristic insane smile and later during the final battle when government forces assault the Wild Seven base. In her final moments, she demonstrates a notable ability to use her psychological damage as a weapon. As commandos breach the fortress wall, Mai is seen packing explosives into her beloved doll. She then throws the doll at the entering soldiers, causing it to detonate and kill them. While throwing the explosive, she is shot at least twice. The blast throws her to the floor, and she can be heard screaming before ultimately being killed off-screen, either by additional gunfire or another explosion. Her death represents a final act of violent resistance against the government that created her, using her most symbolic possession as a tool of revenge.