"Seishun Shiteru Kai!" centers on a group of high school students navigating the complexities of adolescence, relationships, and self-discovery. The narrative primarily revolves around the protagonist, a reserved and introspective student named Haruto, who struggles with feelings of inadequacy and a lack of direction in life. His world changes when he encounters a vibrant and outgoing classmate, Aoi, whose seemingly carefree demeanor masks her own insecurities and struggles. Their contrasting personalities create a dynamic interplay, as they gradually form a bond that challenges both to confront their fears and aspirations.

The story unfolds through a series of interconnected vignettes, exploring the lives of their classmates and friends. Each character is given depth, with their own unique struggles and growth arcs. For instance, there is Rina, a diligent student burdened by familial expectations, and Kenta, a seemingly confident athlete grappling with the pressure to perform. The interactions between these characters highlight themes of friendship, identity, and the pursuit of personal fulfillment.

As the narrative progresses, the group forms a club called the "Seishun Shiteru Kai" (roughly translating to "Youth Awareness Club"), which serves as a space for them to share their thoughts, dreams, and challenges. Through this club, they embark on various activities and projects, each designed to help them better understand themselves and each other. The club becomes a microcosm of their collective journey, symbolizing their shared desire to make the most of their youth.

The plot is driven by both external events and internal conflicts, such as school festivals, exams, and personal crises, which test the characters' resilience and growth. Romantic subplots emerge naturally, adding layers to the relationships without overshadowing the central themes of self-discovery and camaraderie. The story balances moments of humor, drama, and introspection, creating a nuanced portrayal of adolescence that resonates with authenticity.

By the end of the series, the characters have undergone significant personal growth, having confronted their fears, embraced their imperfections, and forged meaningful connections. The narrative concludes on a hopeful note, emphasizing the importance of living authentically and cherishing the fleeting nature of youth. "Seishun Shiteru Kai!" stands as a heartfelt exploration of the trials and triumphs of growing up, offering a relatable and engaging portrayal of the high school experience.