"Cosplay Complex" is a three-episode OVA series that centers around the lives of a group of high school students who are passionate about cosplay. The story is set at East Oizuki Academy, where the Cosplay Club, led by the enthusiastic and determined Chako Martinez, aims to elevate their craft and compete in cosplay events. Chako, a transfer student from Spain, is deeply committed to cosplay and dreams of winning the World Cosplay Championship. Her arrival at the academy sparks a renewed energy within the club, which had been struggling to maintain its relevance.

The club members include Mako, a shy and reserved girl who harbors a secret crush on Chako; Goto, a skilled tailor who handles costume creation; and Reiko, a tomboyish and athletic member who often provides comic relief. Together, they navigate the challenges of balancing their academic lives with their passion for cosplay, often facing obstacles such as limited resources, time constraints, and rivalries with other clubs. The series explores their efforts to improve their skills, create intricate costumes, and prepare for competitions, all while dealing with interpersonal dynamics and personal growth.

The narrative is driven by the club's preparation for the upcoming World Cosplay Championship, which serves as the ultimate goal for Chako and her team. Along the way, they encounter various rivals, including the wealthy and arrogant Mariko, who leads a competing cosplay group. The series highlights the dedication and creativity required for cosplay, as well as the camaraderie and occasional conflicts that arise within the group. While the tone is lighthearted and comedic, it also touches on themes of perseverance, teamwork, and the pursuit of one's passions.

The characters' interactions and development are central to the story, with each member of the Cosplay Club contributing their unique strengths and personalities to the group's efforts. Chako's unwavering determination inspires her teammates, while Mako's quiet support and Goto's technical expertise play crucial roles in their success. The series balances its focus on cosplay with moments of humor and slice-of-life elements, creating a narrative that appeals to fans of both comedic and character-driven anime. Overall, "Cosplay Complex" offers a glimpse into the world of cosplay through the lens of a group of dedicated high school students striving to achieve their dreams.