"Onee-chan wa Game o Suru to Hito ga Kawaru Onee-chan" centers on the relationship between two siblings, Yuu and his older sister, Aoi. Aoi is a diligent and responsible college student who excels academically and maintains a composed demeanor. However, her personality undergoes a dramatic transformation when she plays video games, becoming aggressive, competitive, and entirely absorbed in the virtual world. This stark contrast between her usual self and her gaming persona creates a dynamic and often humorous interplay between the siblings.

Yuu, the younger brother, serves as the narrative’s grounding perspective. He observes and interacts with Aoi’s dual personalities, often finding himself caught in the chaos she creates during her gaming sessions. The story explores their daily lives, focusing on how Aoi’s gaming habits influence their relationship and the situations they encounter. The manga delves into themes of sibling bonds, personal identity, and the impact of hobbies on behavior, all while maintaining a lighthearted and comedic tone.

The plot progresses through episodic scenarios, each highlighting Aoi’s exaggerated gaming antics and Yuu’s attempts to manage or mitigate the fallout. These scenarios often involve misunderstandings, exaggerated reactions, and comedic misunderstandings, driven by Aoi’s intense immersion in gaming culture. The series balances its humor with moments of genuine warmth, showcasing the siblings’ affection for one another despite their differences.

Supporting characters, such as Aoi’s friends and fellow gamers, occasionally appear, adding variety to the interactions and further emphasizing Aoi’s contrasting personalities. The manga’s structure relies on its episodic nature, with each chapter presenting a self-contained story that contributes to the overall exploration of the siblings’ relationship and Aoi’s gaming-induced transformations. The narrative remains grounded in its focus on family dynamics, using humor and relatable scenarios to engage readers.