Read manga: Black Diamond (Fujisawa Tohru)

manga
Summary:

After being reformed by the GTO, Eikichi Onizuka, the Twins of Terror, Riko and Miko Sakaki, leave their past behind and become members of the Disciplinary Committee at their school, Chigasaki Kahoku Private Academy, helping fellow students in need through an SOS messaging system. When an illegal prostitution auction ring is uncovered at their school, the twins set out to restore peace to their school and punish those responsible, GTO-style!Spin-off of GTO - Shonan 14 Days.