FISH
FISH, nicknamed Puffy, is an elder techno-mage, last of the Open clan. He is the teacher of Girl.
Puffy during a lesson with Girl
For the entirety of his life, Puffy was present on MATACORP's list of top 10 most wanted hackers. A trait that Girl would inherit.
Cynical, paranoid and mostly disillusioned, he's set on educating Girl to the best of his abilities in order for her to become his legacy, and once he's gone, the last of the Open clan.
History
Little is known about Puffy's life before the events of Techno-Mage, but it is suggested he is at least 250 years old. After MATACORP took over the entirety of what remained of the world and began hunting down FOSS-affiliated individuals, most of the Open clan was wiped out. Puffy joined the FOSS resistance and began teaching gifted hackers up until the Corpo-Foss war.
After the Battle of King's Hold, the last student of the FISH died, and Puffy retreated from public life, accepting no further students until he was approached by Girl 80 years later.