"Nana Maru San Batsu," also known as "7O3X," is a manga series that centers around competitive quiz bowl, blending intellectual challenges with character-driven drama. The protagonist, Koshiyama Shiki, is a first-year high school student with a deep passion for trivia and a remarkable memory. Initially, Shiki views quiz bowl as a casual hobby, but his perspective shifts when he joins his school's quiz bowl team, the Fujimidai High School Quiz Bowl Club. The club is led by the charismatic and highly skilled Mari Fukami, who becomes a mentor figure for Shiki and the other members.

The narrative explores the dynamics of the team as they prepare for and compete in various quiz bowl tournaments. Each member brings unique strengths and personalities to the group, creating a diverse and engaging ensemble. Shiki's journey is marked by his growth from a novice to a formidable competitor, driven by his love for knowledge and the thrill of competition. Alongside Shiki, key characters include the analytical and strategic Fukami, the energetic and determined Chisato Mikuriya, and the quiet but brilliant Gakuto Sasajima.

The series delves into the intricacies of quiz bowl, highlighting the importance of quick thinking, teamwork, and a broad knowledge base. Matches are depicted with tension and excitement, showcasing the mental agility required to excel in the sport. The story also touches on the personal lives and motivations of the characters, adding depth to their interactions and development. Themes of perseverance, friendship, and the pursuit of excellence are woven throughout the narrative, making "Nana Maru San Batsu" a compelling exploration of both intellectual and emotional growth.