"Katsu!" is a sports manga centered around boxing, written and illustrated by Mitsuru Adachi. The story revolves around Katsuki Adachi, a high school student whose life takes a dramatic turn when he discovers his family's connection to a local boxing gym. Katsuki's father, a former boxer, had abandoned the sport and his family years earlier, leaving behind a legacy that Katsuki initially wants nothing to do with. However, after a chance encounter with a girl named Hiroko, who is passionate about boxing, Katsuki reluctantly begins training at the gym.

As Katsuki delves into the world of boxing, he discovers a natural talent for the sport. His journey is marked by rigorous training, personal growth, and a series of matches that test his skills and determination. Along the way, he forms bonds with fellow boxers, including Hiroko, who becomes both a romantic interest and a source of motivation. Katsuki's rivalry with his estranged father, who reemerges as a prominent figure in the boxing world, adds a layer of emotional complexity to the narrative.

The manga explores themes of perseverance, family, and self-discovery, with a focus on the physical and mental challenges of boxing. Katsuki's progression from a reluctant novice to a dedicated athlete is depicted through his interactions with trainers, opponents, and friends. The story balances intense boxing matches with moments of humor and character development, creating a well-rounded portrayal of the sport and its impact on the characters' lives. Through its engaging plot and relatable characters, "Katsu!" offers a compelling look at the world of competitive boxing and the personal journeys of those who pursue it.