Mito Freecss is Gon's adopted mother, and cousin to Ging Freecss. In the manga Mito did not want Gon to become a Hunter because Ging only came back home once after he took the Hunter's exam. She did not want Gon to leave his family like Ging did. In the manga, Ging is Mito's cousin. However in the anime and novelization, Mito was made into the sister of Gon's mother, making Ging her brother-in-law. Mito was angry with Ging because he left her sister all alone at home and she had to watch her sister look sadly out of the window in hope of her husband returning. Her sister gave birth to Gon and died soon afterwards without seeing her husband ever again. Mito did not want Gon to become a Hunter who did not care about his family like his father. As such, she fights and wins for custody over Gon. However, now that Gon has left, she tries he best to support him in his journey.
Mito is a kind woman that accepts Killua as one of Gon's friends despite learning that he is an assassin, and she feels that people must do everything they can to save another's life. When Gon and Killua found a wounded animal in the forest, Mito slapped Killua for suggesting to kill it and put it out of its misery, and because of this, they came up with the alternate solution of healing it with their nen.