Mari (マリ, Mari) is a young girl that lives in Entotsu City, who's parents work at the excavation.
Mari used a rock to attack Government men, who were talking with Jio and Ruby, telling them to return her parents. One of the men decided to punish her and tried hitting her, but Jio interfered and stopped him. In the fight between Jio and the government men, Jio again saved her and run with her in the steams.
Jio asked her why did she attacked them with a rock, and Mari told him that her parents are ill, but still were forced to work in the excavation and still haven't returned.
Later when Ball and his friend were fighting Jio, she stopped Jio from beating them. She also revealed that Ball is not an OPT, but wants to be one and pretends to be such.