Naruko Yokoshima

Naruko has neck-length reddish brown hair, dark brown eyes, she is roughly equal to Takatoshi Tsuda's height or slightly taller in terms of height and she has a sizable bust she is proud of (though it is still apparently less buxom than Aria's).

As a teacher, she does not have to wear a uniform and is normally seen in the same outfit: a purple long-sleeved shirt with white sleeves and a white collar, tight greyish trousers, a loose hanging belt that is normally around her hips and a single blue bracelet on her left wrist.

While attractive, her perverted personality is a major turn-off for people like Tsuda (who would never let her get away with anything) and the Beach Playboy (who was scared off by how aggressive she was).

Naruko is an incredibly perverted woman who is even more so than Aria Shichijō and Shino Amakusa. She apparently has many lovers and aggressively seeks out younger guys, including her male students. She also happily talks about sex-related topics openly, including her various fetishes that include (among other things) bondage and outdoor sex. She is often portrayed as unreliable and useless as an educator, to the point she was allegedly put in charge of the Student Council because they were so competent they could easily make up for her incompetence.

However, she also has some hidden depths. She often complains about not being able to settle down (25 often being stated as the age a Japanese woman is no longer suitable for marriage) and occasionally shown to like children. In addition, she is a reasonably experienced teacher (at least when dealing with emergencies) and quickly took charge of a search when Suzu Hagimura accidentally got separated from her group during a trip to Osaka.

(Source: Seitokai Yakuindomo Wiki)