"Daidassō March" is a manga series that centers on the life of a young girl named Natsumi, who is thrust into the world of competitive long-distance running after a series of personal and familial challenges. The story begins with Natsumi, a high school student, struggling to find her place in life following the sudden death of her father, a former marathon runner. Her father's passion for running had always been a source of inspiration, but Natsumi had never considered pursuing it herself until she discovers a hidden journal detailing his training methods and aspirations.

Motivated by her father's unfulfilled dreams and her own desire to honor his memory, Natsumi decides to join her school's track and field team. Initially, she faces significant hurdles, including her lack of experience, physical limitations, and skepticism from her peers and coaches. However, her determination and relentless work ethic gradually earn her the respect of her teammates and mentors. The narrative delves into the rigorous training regimens, the physical and mental toll of long-distance running, and the camaraderie and rivalries that develop within the team.

As Natsumi progresses, she encounters several key figures who shape her journey. Among them is her coach, a former professional runner who recognizes her potential and pushes her to excel, and a rival runner from a competing school who becomes both a formidable opponent and a source of motivation. The series also explores Natsumi's relationships with her family, particularly her mother, who initially disapproves of her decision to run but eventually comes to support her daughter's ambitions.

The plot is structured around Natsumi's participation in various races, each serving as a milestone in her development as an athlete and as a person. These races are depicted with a focus on the strategic and psychological aspects of competition, highlighting the importance of pacing, endurance, and mental fortitude. The series also addresses broader themes such as perseverance, self-discovery, and the impact of parental influence on personal goals.

Throughout the manga, Natsumi's growth is evident not only in her athletic achievements but also in her evolving understanding of herself and her motivations. The narrative balances intense sports action with moments of introspection and emotional depth, creating a well-rounded portrayal of a young athlete's journey. "Daidassō March" ultimately presents a compelling exploration of the challenges and rewards of pursuing a dream, set against the backdrop of the demanding world of long-distance running.