Kenichi Shirahama, a timid and bullied high school student, begins training in martial arts to become stronger and protect himself. His life changes when he meets Miu Furinji, a skilled martial artist who introduces him to Ryōzanpaku, a dojo run by six eccentric and highly skilled martial arts masters. Each master specializes in a different discipline, including karate, Chinese martial arts, judo, Muay Thai, weapons combat, and assassination techniques. Under their rigorous and often unconventional training, Kenichi gradually develops his skills and confidence.

The narrative follows Kenichi’s journey as he faces various challenges, including rival martial artists, criminal organizations, and personal growth. His progress is tested through numerous battles, where he must apply the techniques and philosophies taught by his masters. Alongside Miu, who serves as both a mentor and a romantic interest, Kenichi navigates the complexities of the martial arts world, which includes rival dojos, underground fighting rings, and powerful adversaries seeking to exploit or eliminate him.

Key antagonists include Ragnarok, a gang of delinquent martial artists, and Yami, a shadowy organization with ties to ancient martial arts traditions. These groups pose significant threats, forcing Kenichi to continually push his limits. The series explores themes of perseverance, discipline, and the moral responsibilities of wielding strength. Kenichi’s growth is not only physical but also ethical, as he learns to balance his newfound power with compassion and justice.

The supporting cast includes the Ryōzanpaku masters, each with distinct personalities and backstories that add depth to the narrative. Miu Furinji, the granddaughter of the dojo’s founder, plays a central role as Kenichi’s primary motivator and equal. Other characters, such as Kenichi’s classmates and rivals, contribute to the story’s dynamic, creating a blend of action, humor, and camaraderie. The series combines intense martial arts battles with lighthearted moments, maintaining a balance between serious combat and comedic interactions.