Sayuri Ookami

A shady third-year student who longs to make Shinobu hers and hers alone. Ookami is the top of her class and is well-respected by her teachers as well as most of her underclassmen for her model behavior but also proves to be a calculated schemer in her pursuit of Shinobu. She attempts to seduce Shinobu in an empty room but is repeatedly, yet, half-heartedly refused because Shinobu doesn't want to hurt her. Her true plan was to get Momoko to lose her temper and get herself expelled so that she would be separated from Shinobu. Her plan is realized when Momoko attacks her with a fire extinguisher. The matter is settled quietly out of court and Momoko is allowed to stay but she chooses to leave anyway. Despite the fact that her plan ultimately succeeded it proves to be in vain as Momoko and Shinobu consummate their feelings several months later.(From Wikipedia)