Member of the Cyclops, the original inhabitants of the O-Parts Hunter Planet, Mei had a significant crush on Jio during and shortly after the time-skip. She viewed any girl who interacted with Jio as competition and even considered Cross a rival, acknowledging Cross's mature beauty. Surprisingly, she formed a quick friendship with Ruby despite feeling envious of Ruby's beauty and Jio's feelings for her. Mei first encountered Jio when her village nursed him back to health during the time-skip. She joined Jio's party by sneaking in and has been traveling with them ever since. Her older brother, Tsubame, the former leader of the Cyclops village, disappeared around the time Jio arrived.
During a battle with Tsubame, Mei unlocked the power of her third eye and, with Ball's assistance, managed to defeat her brother. After witnessing Ball fight the transformed Tsubame, Mei realized she had used Jio as a substitute for her lost brother and developed affection and love for Ball. It was revealed that Mei's father was Kirin and Kujaku's cousin, making Kirin and Kujaku her second cousins. Mei enjoys sweets and found her grandfather, the mayor of her village, extremely annoying.
Inside the Zenom base, Mei, Kirin, and Jajamaru fought against Kujaku. Using her third eye, she took control of Kirin's katana and helped deliver the final blow. Mei witnessed the near-Armageddon event and was one of the last to hear Jio Freed's voice before he vanished into the void. Years later, Mei settled down with Ball and had twins. Although her face is not shown, her hair and outfit are recognizable. She tells her children stories from their youth and puts them to bed, placing the book next to the Tricky O-part.
At the end of the series, it is revealed that Mei and Ball got married and had two children: a son with Mei's hair and third eye, and a daughter with Ball's black hair and Mei's regular eyes. Both twins have the potential to become OPTs, but based on genetic inheritance and past examples, it is likely that only one will follow this path. The twins wear scarves identical to Jio Freed's, reflecting attributes inherited from both parents, similar to Kirin and Kujaku.
