The long suffering Mrs. Onizuka tries her hardest to tolerate her son Eikichi’s punkass behavior, but eventually has to kick him out to keep her apartment. She herself is rather a tough lady, and apparently had her son at a young age. She works as a club hostess, according to the GTO B.A.D. Action guidebooks. Her first name is never revealed, and it is unknown if Onizuka is her maiden name, or if she was ever married.
Eikichi’s dad- the former head of the SPEED motorbike gang- is never seen, but he doesn’t seem to live with them. Mrs. Onizuka is still an attractive looking woman, with long brown(?) wavy hair. She does seem to dress older though.
In GTO: Shonan 14 Days it is revealed she has moved to Hawaii; in chapter 7, Onizuka mentions that his father was a womaniser, which probably explains his absence during the original Shonan Junai Gumi series.