Kaoru Kamata

She is Jun Kamata’s younger sister. She first appears when the Oni-Baku-gumi arrange their ‘get-together’. Her brother bumps into her and recognises her (apparently they haven’t seen each other for a while) and spends the whole evening trying to keep the others away. Eikichi is obsessed with Kaoru and doesn’t pay any attention to Itou at all, which results in a fight with Tsukai. In actuality, however, ‘she’ is really male, which shocks Onizuka when he finds out. Kaoru appears during the Natsu saga, and tells Eikichi about her brother’s predicament. She is something of a minor character. Kaoru first chose to disguise himself to get money from the boys that he brings to his house by hitting their whole body, but eikichi beats him to search kaoru in the house, and kaoru then fell in love of him... (Source: Wikipedia)