"Stella Women's Academy, High School Division Class C3" centers on Yura Yamato, a timid and reserved first-year high school student who enrolls at the prestigious Stella Women's Academy. Seeking to break out of her shell, Yura stumbles upon the school's C3 Club, a group dedicated to airsoft, a tactical shooting sport using replica firearms. Initially hesitant, Yura is drawn in by the club's charismatic president, Sonora Kashima, who encourages her to join and experience the thrill of the game.

The narrative explores Yura's growth as she navigates the challenges of airsoft, from learning the basics of handling equipment to developing strategic thinking and teamwork. The club members, including the competitive and skilled Rento Kirishima, the cheerful and supportive Honoka Mutsu, and the stoic yet dependable Karila Hatsuse, each bring unique personalities and skills to the group. Together, they participate in matches against rival schools and clubs, fostering camaraderie and personal development.

As Yura becomes more involved, she begins to confront her insecurities and discovers a newfound confidence through the sport. The series balances lighthearted moments of friendship and humor with the intensity of airsoft battles, highlighting the importance of perseverance and self-discovery. The storyline also delves into the dynamics within the club, addressing conflicts and rivalries while emphasizing the value of trust and collaboration.

The anime portrays airsoft not just as a competitive activity but as a means of personal growth, with Yura's journey serving as the emotional core. Through her experiences, the series captures the challenges and rewards of stepping out of one's comfort zone and finding a sense of belonging. The narrative remains grounded in its focus on character development and the evolving relationships within the C3 Club, offering a blend of action, drama, and slice-of-life elements.