Natsuki Crisis

Natsuki is the top female karateka in her high school. Beautiful and cheerful, she charms most people she meets. Most of the young men in her class would dearly like to be the object of her affection but she saves her passion for karate. Unfortunately, all the big ugly thugs she comes across want to fight her so she's always finding practical application for her karate skills. As the series continues and her opponents get grimmer, Natsuki learns techniques from Akido and Judo and develops a special Ki energy blast that doubles the strength of her punches. She may not be able to smash walls like some of her opponents but her special N.G. Bomber usually sends her opponents flying.
(Source: AniDB)