In the comic strip, the main character, Toshi, an ordinary high school student, spent his days being fed and taught by a beautiful neighbor named Yuu-neesan, who lived near his house instead of his parents, who were rarely home. The older sister was kind and perfect as an adult. However, she had a hidden side as her personality completely changes when it comes to games... Games aren't just fun! Big sister gets angry, gets naked, and spares no effort! Toshi gets trapped in her personality duality!
The story of Onee-chan wa Game o Suru to Hito ga Kawaru Onee-chan revolves around this unique dynamic, exploring the impact of gaming on Yuu-neesan personality and the relationships within the story. It delves into the idea of how a simple pastime can bring about significant changes in an individual's behavior and outlook on life.