Tetsu Kenji Kousuke

An action comedy depicting the exploits of martial artist Tsuyuki Kousuke. As the future director of the Tsuyuki Martial Arts Gym, Kousuke undergoes strict daily training from his grandfather, Denjuurou, on top of attending high school. One day, he saves a strong-willed girl named Minatsu who had gotten mixed up with some delinquents, but...!?

(Source: mangaupdates.com)