Saki Tabaruzaka

Saki is another student of Shuuhou Seiha Private School, who is in lust with Naeka. She is so obsessed, she jealously attacks anyone else who attempts to see Naeka in the nude before she does. Saki's efforts are sometimes thwarted by Kogarashi, though he refuses to harm her directly. So far, no character has referred to Saki by name in the anime.
Source: Wikipedia.