"I'm Glad I Could Keep Running" centers on the journey of Haruto, a high school student who struggles with self-doubt and a lack of direction in life. After a chance encounter with a former track star, Riku, Haruto is inspired to join the school's track and field team. Initially hesitant and out of shape, Haruto gradually discovers a passion for running, driven by Riku's mentorship and the camaraderie of his teammates. The narrative explores Haruto's growth as he trains for regional competitions, facing physical and emotional challenges along the way.

The story delves into the dynamics of the track team, highlighting the contrasting personalities and motivations of its members. Riku, now a coach due to a career-ending injury, serves as a guiding figure, balancing tough love with genuine care for his athletes. Other key characters include Aoi, a fiercely competitive sprinter with a troubled past, and Yuna, a long-distance runner who struggles with self-confidence despite her natural talent. The interactions between the characters reveal their individual struggles and aspirations, creating a layered portrayal of teamwork and personal growth.

As the season progresses, Haruto and his teammates prepare for the regional championships, a pivotal event that tests their resolve and unity. The series emphasizes the physical and mental demands of competitive running, portraying the highs of victory and the lows of defeat with equal weight. Themes of perseverance, self-discovery, and the importance of support systems are woven throughout the narrative, culminating in a climactic race that serves as both a personal and collective triumph for the team. The story concludes on a reflective note, underscoring the value of persistence and the transformative power of pursuing one's passions.