Kōichi Asakura is the protagonist of Eren the Southpaw. He works as a male designer at the major advertising agency Meguro Advertising Company. During his high school years, he was shocked to see graffiti on the wall of an art museum and discovered it was created by a left-handed high school girl named Eren Yamagishi. This encounter with her overwhelming talent ignited a sense of rivalry in him and set him on the path to become a designer. Despite his dedication and hard work, he struggles to gain recognition at his job and often finds himself overshadowed by those with natural talent, which leads to a deep-seated inferiority complex. He knows his own limits but burns to rise above them, driven by a desire to leave his mark on the world even if he is not a born artist. He is frustrated by his circumstances and grapples with the harsh realities of the creative industry, where he must persist as an ordinary person among prodigies. His narrative focuses on the persistence required to survive in such an environment. He shares a complex, competitive, and admiring bond with Eren Yamagishi, whom he views as the embodiment of the genius he lacks. He also works closely with colleagues such as Sayuri Kato within the high-pressure environment of the ad agency. His character arc involves moving from a desperate need for validation to finding his own worth within the professional creative landscape, eventually learning to leverage his persistence and perspective as a non-genius to achieve success on his own terms. His abilities include his technical skill as a designer and his unbreakable passion, which fuels his continued struggle to become something more.