Koutarou Breakthrough!

A high school aged karate expert who is descended from a long line of ninja. While he may be a fighting genius, he lacks common sense and any inhibitions whatsoever. He spends most of his time getting into trouble with school officials, and trying to steal girls' panties; especially Mayumi's. He is very protective of three things: his long hair, his panty collection, and Mayumi.

(Source: Wikpedia)