She is the new remedial teacher. When she was a sickly child, Happousai trained her in what she thought was "best gymnastics". In fact, he taught her the Happou-goen-satsu "ki" absorption technique to take out the opposition to his panty raids (he taught her this so that she would stop the nurses from chasing him after he stole their underwear).
She is a child-like English teacher, with an awesome chi-sucking attack, which temporarily turns her into the best-shaped babe in the series. In child form has many child-like attributes, like wanting sweets, playing with toys etc, and she also wants to marry Soun. While the students are afraid of Hinako's powers, since the 'little girl' doesn't use it that often, they take advantage of her child-nature and play around in class, and call her 'Hina-chan-sensei'.
Personality: Having a split-personality often causes her difficulties in trying to what task is at hand - e.g. her students aren't particularly afraid of her (except when she starts using her special powers), and her child body and nature reduce her concentration, and readily side-track her.
However, she is very serious in wanting to be a good teacher, making children behave properly, and also in wanting to marry Soun - even though his daughters made it very clear they don't want a new mother. She is still persistent, though she does have trouble not being able to be an adult all the time.
Higuma was the new teacher at Furinkan High School. Most of the students thought he'd be another tough teacher, but Higuma turned out to be really nice to the students. He tried to get them to "appreciate their youth", before he left to go help another school.